diff --git a/config/config.php b/config/config.php
index 8d10905d51..173a4cd59f 100644
--- a/config/config.php
+++ b/config/config.php
@@ -231,3 +231,8 @@ else
     unset($config->maxVersion);
     unset($config->ipdVersion);
 }
+
+/* Set zin config. */
+$config->zin = new stdClass();
+$config->zin->mode       = 'compatible';     // 启用兼容 18.x 模式。
+$config->zin->extraCSS   = 'compatible.css'; // 额外的 CSS 样式文件。
diff --git a/lib/zin/config.php b/lib/zin/config.php
index 1c0be501e8..630643653f 100644
--- a/lib/zin/config.php
+++ b/lib/zin/config.php
@@ -16,7 +16,7 @@ function loadConfig()
 {
     global $app, $config;
 
-    $config->zin = new \stdClass();
+    if(!isset($config->zin)) $config->zin = new \stdClass();
 
     $config->zin->lang     = $app->getClientLang();
     $config->zin->wgVer    = isset($config->wgVer) ? $config->wgVer : '1';
diff --git a/lib/zin/wg/pagebase/v1.php b/lib/zin/wg/pagebase/v1.php
index b2d9317086..26efeeb3ea 100644
--- a/lib/zin/wg/pagebase/v1.php
+++ b/lib/zin/wg/pagebase/v1.php
@@ -64,7 +64,7 @@ class pageBase extends wg
         $themeName  = $app->cookie->theme;
         $zuiPath    = $config->zin->zuiPath;
 
-        $jsConfig->zin     = true;
+        $jsConfig->zin = (isset($config->zin->mode) && $config->zin->mode) ? $config->zin->mode : true;
 
         $headImports = array();
         if($zui)
@@ -73,6 +73,8 @@ class pageBase extends wg
             $headImports[] = h::importCss($zuiPath . 'themes/' . $themeName . '.css', setID('zuiTheme'));
             $headImports[] = h::importJs($zuiPath . 'zui.zentao.umd.cjs', setID('zuiJS'));
             $headImports[] = h::jsCall('$.setLibRoot', $zuiPath);
+
+            if(isset($config->zin->extraCSS) && $config->zin->extraCSS) $headImports[] = h::importCss($webRoot . 'js/zui3/' . $config->zin->extraCSS);
         }
         $headImports[] = h::jsVar('window.config', $jsConfig, setID('configJS'));
         if($zui) $headImports[] = h::importJs($webRoot . 'js/zui3/zin.js', setID('zinJS'));
diff --git a/www/js/zui3/compatible.css b/www/js/zui3/compatible.css
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/www/js/zui3/zin.js b/www/js/zui3/zin.js
index edafb9021b..38cddf89aa 100644
--- a/www/js/zui3/zin.js
+++ b/www/js/zui3/zin.js
@@ -7,7 +7,7 @@
     const currentMethod = config.currentMethod;
     const isIndexPage   = currentModule === 'index' && currentMethod === 'index';
     const isInAppTab    = parent.window !== window;
-    const is18version   = true;
+    const is18version   = config.zin === 'compatible';
 
     const selfOpenList = new Set('index|tutorial|install|upgrade|sso|cron|misc|user-login|user-deny|user-logout|user-reset|user-forgetpassword|user-resetpassword|my-changepassword|my-preference|file-read|file-download|file-uploadimages|report-annualdata|misc-captcha|execution-printkanban|traincourse-playvideo'.split('|'));
     const isAllowSelfOpen = isIndexPage
@@ -46,7 +46,7 @@
     if(isIndexPage) return;
 
     const DEBUG       = config.debug;
-    const is18version = true;
+    const is18version = config.zin === 'compatible';
     const currentCode = window.name.substring(4);
     const isInAppTab  = parent.window !== window;
     const fetchTasks  = new Map();