diff --git a/db/update20.0.sql b/db/update20.0.sql
index e8bbe6fb8a..f52dc6224d 100644
--- a/db/update20.0.sql
+++ b/db/update20.0.sql
@@ -24,10 +24,10 @@ CREATE TABLE `zt_storygrade` (
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 ALTER TABLE `zt_story` ADD `grade` smallint(6) NOT NULL AFTER `parent`;
-ALTER TABLE `zt_story` ADD `path` varchar(255) NULL AFTER `grade`;
-update zt_story set grade = 1, path = concat(',', id, ',') where type != 'story';
-update zt_story set grade = 1, path = concat(',', id, ',') where type = 'story' and parent <= 0;
-update zt_story set grade = 2, path = concat(',', parent, ',', id, ',') where type = 'story' and parent > 0;
+ALTER TABLE `zt_story` ADD `top` mediumint NOT NULL DEFAULT '0' AFTER `parent`;
+update zt_story set grade = 1, parent = 0, top = id where type != 'story';
+update zt_story set grade = 1, parent = 0, top = id where type = 'story' and parent <= 0;
+update zt_story set grade = 2, top = parent where type = 'story' and parent > 0;
 
 INSERT INTO `zt_config` (`owner`, `module`, `section`, `key`, `value`) VALUES ('system', 'story', '', 'gradeRule', 'stepwise');
 INSERT INTO `zt_config` (`owner`, `module`, `section`, `key`, `value`) VALUES ('system', 'requirement', '', 'gradeRule', 'stepwise');
diff --git a/module/product/js/browse.ui.js b/module/product/js/browse.ui.js
index 08a5e55e03..6c260f7c6f 100644
--- a/module/product/js/browse.ui.js
+++ b/module/product/js/browse.ui.js
@@ -63,11 +63,11 @@ window.renderCell = function(result, info)
         const story = info.row.data;
         let html = '';
         if(typeof modulePairs[story.rawModule] != 'undefined') html += "<span class='label gray-pale rounded-xl clip'>" + modulePairs[story.rawModule] + "</span> ";
-        if(story.parent > 0)
-        {
-            if($.cookie.get('tab') == 'project') html += story.parentName + ' / ';
-            html += "<span class='label gray-pale rounded-xl clip'>" + (storyType == 'requirement' ? 'SR' : childrenAB) + "</span> ";
-        }
+        if(story.parent > 0) if($.cookie.get('tab') == 'project') html += story.parentName + ' / ';
+
+        let gradeLabel = gradeGroup[story.type][story.grade];
+        if(!showGrade && story.grade < 2) gradeLabel = '';
+        if(gradeLabel) html += "<span class='label gray-pale rounded-xl clip'>" + gradeLabel + "</span> ";
         if(story.color) result[0].props.style = 'color: ' + story.color;
         if(html) result.unshift({html});
     }
diff --git a/module/product/ui/browse.html.php b/module/product/ui/browse.html.php
index f68c60bc42..6092400bb5 100644
--- a/module/product/ui/browse.html.php
+++ b/module/product/ui/browse.html.php
@@ -15,6 +15,8 @@ namespace zin;
 data('storyType', $storyType);
 data('activeMenuID', $storyType);
 jsVar('URChanged', $this->lang->story->URChanged);
+jsVar('gradeGroup', $gradeGroup);
+jsVar('showGrade', $showGrade);
 
 $storyCommon       = $storyType == 'requirement' ? $lang->URCommon : $lang->SRCommon;
 $isProjectStory    = $this->app->rawModule == 'projectstory';
diff --git a/module/product/zen.php b/module/product/zen.php
index 78bc0c5027..9dc85c39fc 100644
--- a/module/product/zen.php
+++ b/module/product/zen.php
@@ -1451,6 +1451,10 @@ class productZen extends product
         $projectProducts = $this->getProjectProductList($projectID, $storyType, $isProjectStory);
         list($branchOpt, $branchTagOpt) = $this->getBranchAndTagOption($projectID, $product, $isProjectStory);
 
+        $gradeList  = $this->loadModel('story')->getGradeList('');
+        $gradeGroup = array();
+        foreach($gradeList as $grade) $gradeGroup[$grade->type][$grade->grade] = $grade->name;
+
         /* Set show module by config. */
         $showModule = empty($this->config->product->browse->showModule) ? 0 : $this->config->product->browse->showModule;
         if($isProjectStory) $showModule = empty($this->config->projectstory->story->showModule) ? 0 : $this->config->projectstory->story->showModule;
@@ -1461,6 +1465,8 @@ class productZen extends product
         $this->view->projectID       = $projectID;
         $this->view->project         = $project;
         $this->view->stories         = $stories;
+        $this->view->gradeGroup      = $gradeGroup;
+        $this->view->showGrade       = $storyType == 'story' ? count($gradeGroup[$storyType]) > 2 : count($gradeGroup[$storyType]) > 1;
         $this->view->storyType       = $storyType;
         $this->view->browseType      = $browseType;
         $this->view->isProjectStory  = $isProjectStory;
diff --git a/module/story/model.php b/module/story/model.php
index 41cc961d1f..1bbf860cfb 100644
--- a/module/story/model.php
+++ b/module/story/model.php
@@ -447,8 +447,6 @@ class storyModel extends model
         $storyID = $this->storyTao->doCreateStory($story);
         if(!$storyID) return false;
 
-        $this->dao->update(TABLE_STORY)->set('path')->eq(",{$storyID},")->where('id')->eq($storyID)->exec();
-
         /* Upload files. */
         $this->loadModel('action');
         $this->loadModel('file')->updateObjectID($this->post->uid, $storyID, $story->type);
@@ -466,7 +464,14 @@ class storyModel extends model
         if($bugID)       $this->storyTao->closeBugWhenToStory($bugID, $storyID);
         if(!empty($story->reviewer)) $this->storyTao->doCreateReviewer($storyID, $story->reviewer);
         if(!empty($story->URS))      $this->storyTao->doCreateURRelations($storyID, $story->URS);
-        if(!empty($story->parent))   $this->subdivide($story->parent, array($storyID));
+        if(!empty($story->parent))
+        {
+            $this->subdivide($story->parent, array($storyID));
+        }
+        else
+        {
+            $this->dao->update(TABLE_STORY)->set('top')->eq($storyID)->where('id')->eq($storyID)->exec();
+        }
         if(!empty($story->plan))
         {
             $this->updateStoryOrderOfPlan($storyID, (string)$story->plan); // Set story order in this plan.
@@ -586,7 +591,14 @@ class storyModel extends model
             if(!$storyID) return array();
 
             $this->storyTao->doCreateSpec($storyID, $story);
-            if($story->parent > 0) $this->subdivide($story->parent, array($storyID));
+            if(!empty($story->parent))
+            {
+                $this->subdivide($story->parent, array($storyID));
+            }
+            else
+            {
+                $this->dao->update(TABLE_STORY)->set('top')->eq($storyID)->where('id')->eq($storyID)->exec();
+            }
 
             /* Update product plan stories order. */
             if(!empty($story->reviewer)) $this->storyTao->doCreateReviewer($storyID, $story->reviewer);
@@ -748,10 +760,15 @@ class storyModel extends model
         if($story->grade != $oldStory->grade)
         {
             $gradeDiff = (int)$story->grade - (int)$oldStory->grade;
-            $this->dao->update(TABLE_STORY)->set("grade = grade + $gradeDiff")->where('path')->like($oldStory->path . '%')->andWhere('id')->ne($storyID)->exec();
+            $this->dao->update(TABLE_STORY)
+                      ->set("grade = grade + $gradeDiff")
+                      ->where('top')->eq($oldStory->top)
+                      ->andWhere('grade')->gt($oldStory->grade)
+                      ->andWhere('id')->ne($storyID)
+                      ->exec();
         }
         $parentChanged = $story->parent != $oldStory->parent;
-        if($parentChanged) $this->doChangeParent($storyID, $story, $oldStory->parent, $oldStory->path);
+        if($parentChanged) $this->doChangeParent($storyID, $story, $oldStory->parent);
         if($oldStory->parent > 0) $this->updateParentStatus($storyID, $oldStory->parent, !$parentChanged);
         if($story->parent > 0) $this->updateParentStatus($storyID, $story->parent, !$parentChanged);
 
@@ -1004,12 +1021,11 @@ class storyModel extends model
         }
 
         $this->loadModel('action');
-        $changeGradeList = array();
         foreach($stories as $storyID => $story)
         {
             $oldStory = $oldStories[$storyID];
             if(!$story->grade) $story->grade = $oldStory->grade;
-            $this->dao->update(TABLE_STORY)->data($story)
+            $this->dao->update(TABLE_STORY)->data($story, 'grade')
                 ->autoCheck()
                 ->checkIF($story->closedBy, 'closedReason', 'notempty')
                 ->checkIF($story->closedReason == 'done', 'stage', 'notempty')
@@ -1020,14 +1036,20 @@ class storyModel extends model
             if(dao::isError()) return false;
 
             /* Update story sort of plan when story plan has changed. */
-            if($oldStory->plan != $story->plan) $this->updateStoryOrderOfPlan($storyID, (string)$story->plan, $oldStory->plan);
             if($story->grade != $oldStory->grade)
             {
-                $changeGradeList[$storyID]['oldGrade'] = $oldStory->grade;
-                $changeGradeList[$storyID]['newGrade'] = $story->grade;
+                $gradeDiff = (int)$story->grade - (int)$oldStory->grade;
+                $this->dao->update(TABLE_STORY)
+                     ->set("grade = grade + $gradeDiff")
+                     ->where('top')->eq($oldStory->top)
+                     ->andWhere('grade')->gt($oldStory->grade)
+                     ->andWhere('id')->ne($storyID)
+                     ->exec();
+                $this->dao->update(TABLE_STORY)->set('grade')->eq($story->grade)->where('id')->eq($storyID)->exec();
             }
+            if($oldStory->plan != $story->plan) $this->updateStoryOrderOfPlan($storyID, (string)$story->plan, $oldStory->plan);
             $parentChanged = $story->parent != $oldStory->parent;
-            if($parentChanged) $this->doChangeParent($storyID, $story, $oldStory->parent, $oldStory->path);
+            if($parentChanged) $this->doChangeParent($storyID, $story, $oldStory->parent);
             if($oldStory->parent > 0) $this->updateParentStatus($storyID, $oldStory->parent, !$parentChanged);
             if($story->parent > 0) $this->updateParentStatus($storyID, $story->parent, !$parentChanged);
 
@@ -1049,12 +1071,6 @@ class storyModel extends model
             }
         }
 
-        foreach($changeGradeList as $storyID => $oldStory)
-        {
-            $gradeDiff = $oldStory['newGrade'] - $oldStory['oldGrade'];
-            $this->dao->update(TABLE_STORY)->set("grade = grade + $gradeDiff")->where('path')->like("%,{$storyID},%")->andWhere('id')->ne($storyID)->exec();
-        }
-
         $this->loadModel('score')->create('ajax', 'batchEdit');
         foreach($unlinkPlans as $planID => $stories) $this->action->create('productplan', $planID, 'unlinkstory', '', $stories);
         foreach($link2Plans as $planID => $stories)  $this->action->create('productplan', $planID, 'linkstory', '', $stories);
@@ -1334,10 +1350,9 @@ class storyModel extends model
         /* Set parent to child story. */
         foreach($SRList as $childStoryID)
         {
-            $path = rtrim($oldStory->path, ',') . ",$childStoryID,";
             $this->dao->update(TABLE_STORY)
                  ->set('parent')->eq($storyID)
-                 ->set('path')->eq($path)
+                 ->set('top')->eq($oldStory->top)
                  ->where('id')->eq($childStoryID)
                  ->exec();
         }
@@ -2043,11 +2058,10 @@ class storyModel extends model
      * 获取需求的所有子需求ID。
      *
      * @param  int    $storyID
-     * @param  bool   $includeSelf
      * @access public
      * @return array
      */
-    public function getAllChildId(int $storyID, bool $includeSelf = true): array
+    public function getAllChildId(int $storyID): array
     {
         if($storyID == 0) return array();
 
@@ -2055,9 +2069,9 @@ class storyModel extends model
         if(empty($story)) return array();
 
         $children = $this->dao->select('id')->from(TABLE_STORY)
-            ->where('path')->like($story->path . '%')
-            ->andWhere('deleted')->eq(0)
-            ->beginIF(!$includeSelf)->andWhere('id')->ne($storyID)->fi()
+            ->where('deleted')->eq(0)
+            ->andWhere('top')->eq($story->top)
+            ->andWhere('grade')->gt($story->grade)
             ->fetchPairs();
 
         return array_keys($children);
@@ -2214,10 +2228,10 @@ class storyModel extends model
      * @param  string|array $modules
      * @param  string       $fieldName
      * @param  string       $fieldValue
-     * @param  string       $type         requirement|story
+     * @param  string       $type       requirement|story
      * @param  string       $orderBy
      * @param  object       $pager
-     * @param  string       $operator     equal|include
+     * @param  string       $operator   equal|include
      * @access public
      * @return array
      */
@@ -4636,7 +4650,11 @@ class storyModel extends model
      */
     public function getGradeList($type = 'story'): array
     {
-        return $this->dao->select('*')->from(TABLE_STORYGRADE)->where('type')->eq($type)->orderBy('grade_asc')->fetchAll();
+        return $this->dao->select('*')->from(TABLE_STORYGRADE)
+            ->where('1=1')
+            ->beginIF($type)->andWhere('type')->eq($type)->fi()
+            ->orderBy('grade_asc')
+            ->fetchAll();
     }
 
     /**
@@ -4719,7 +4737,7 @@ class storyModel extends model
     public function checkGrade(object $story, object $oldStory, string $method = 'edit')
     {
         $maxGrade = $this->dao->select('max(grade) as maxGrade')->from(TABLE_STORY)
-             ->where('path')->like("{$oldStory->path}%")
+             ->where('top')->eq($oldStory->top)
              ->andWhere('deleted')->eq('0')
              ->fetch('maxGrade');
 
diff --git a/module/story/tao.php b/module/story/tao.php
index a91b75a560..03062a0229 100644
--- a/module/story/tao.php
+++ b/module/story/tao.php
@@ -817,14 +817,11 @@ class storyTao extends storyModel
      * @param  int       $storyID
      * @param  object    $story
      * @param  int       $oldStoryParent
-     * @param  string    $oldStoryPath
      * @access protected
      * @return void
      */
-    protected function doChangeParent(int $storyID, object $story, int $oldStoryParent, string $oldStoryPath)
+    protected function doChangeParent(int $storyID, object $story, int $oldStoryParent)
     {
-        if($story->parent == $oldStoryParent) return;
-
         $this->loadModel('action');
         if($oldStoryParent > 0)
         {
@@ -841,9 +838,9 @@ class storyTao extends storyModel
 
         if($story->parent > 0)
         {
-            $parentStory    = $this->dao->select('*')->from(TABLE_STORY)->where('id')->eq($story->parent)->fetch();
-            $story->path    = rtrim($parentStory->path, ',') . ',' . $storyID . ',';
-            $children       = $this->dao->select('id')->from(TABLE_STORY)->where('parent')->eq($story->parent)->andWhere('deleted')->eq(0)->fetchPairs('id', 'id');
+            $parentStory = $this->dao->select('*')->from(TABLE_STORY)->where('id')->eq($story->parent)->fetch();
+            $newTop      = $parentStory->top;
+            $children    = $this->dao->select('id')->from(TABLE_STORY)->where('parent')->eq($story->parent)->andWhere('deleted')->eq(0)->fetchPairs('id', 'id');
             $this->dao->update(TABLE_STORY)
                 ->set('childStories')->eq(implode(',', $children))
                 ->set('lastEditedBy')->eq($this->app->user->account)
@@ -859,16 +856,12 @@ class storyTao extends storyModel
         }
         else
         {
-            $story->path = ",$storyID,";
+            $newTop = $storyID;
         }
 
         $childStories = $this->getAllChildId($storyID);
-        foreach($childStories as $childStoryID)
-        {
-            $oldChildPath = $this->dao->select('path')->from(TABLE_STORY)->where('id')->eq($childStoryID)->fetch('path');
-            $newChildPath = str_replace($oldStoryPath, $story->path, $oldChildPath);
-            $this->dao->update(TABLE_STORY)->set('path')->eq($newChildPath)->where('id')->eq($childStoryID)->exec();
-        }
+        if($childStories) $this->dao->update(TABLE_STORY)->set('top')->eq($newTop)->where('id')->in($childStories)->exec();
+        $this->dao->update(TABLE_STORY)->set('top')->eq($newTop)->where('id')->eq($storyID)->exec();
     }
 
     /**