diff --git a/framework/helper.class.php b/framework/helper.class.php
index aedb5de5bd..b2763a5ec6 100644
--- a/framework/helper.class.php
+++ b/framework/helper.class.php
@@ -75,4 +75,40 @@ class helper extends baseHelper
         $replacements = array("\\\\", "\\/", "\\\"", "\'", "\\n", "\\r", "\\t",  "\\f",  "\\b", "\\u");
         return str_replace($escapers, $replacements, $json);
     }
+
+    /**
+     * Convert encoding.
+     * 
+     * @param  string $string 
+     * @param  string $fromEncoding 
+     * @param  string $toEncoding 
+     * @static
+     * @access public
+     * @return string
+     */
+    static public function convertEncoding($string, $fromEncoding, $toEncoding = 'utf-8')
+    {
+        $toEncoding = str_replace('utf8', 'utf-8', $toEncoding);
+        if($fromEncoding == $toEncoding) return $string;
+        if(function_exists('mb_convert_encoding'))
+        {
+            /* Remove like utf-8//TRANSLIT. */
+            $position = strpos($toEncoding, '//');
+            if($position !== false) $toEncoding = substr($toEncoding, 0, $position);
+
+            /* Check string encoding. */
+            $encoding = strtolower(mb_detect_encoding($string, array('ASCII','UTF-8','GB2312','GBK','BIG5')));
+            if($encoding == $toEncoding) return $string;
+            return mb_convert_encoding($string, $toEncoding, $fromEncoding);
+        }
+        elseif(function_exists('iconv'))
+        {
+            $convertString = @iconv($fromEncoding, $toEncoding, $string);
+            /* iconv error then return original. */
+            if(!$convertString) return $string;
+            return $convertString;
+        }
+
+        return $string;
+    }
 }
diff --git a/module/file/control.php b/module/file/control.php
index eed49afc72..2e72eda9a3 100644
--- a/module/file/control.php
+++ b/module/file/control.php
@@ -166,17 +166,7 @@ class file extends control
         $this->view->fields = $this->post->fields;
         $this->view->rows   = $this->post->rows;
         $output = $this->parse('file', 'export2csv');
-        if( $this->post->encode != "utf-8")
-        {
-            if(function_exists('mb_convert_encoding'))
-            {
-                $output = @mb_convert_encoding($output, $this->post->encode, 'utf-8');
-            }
-            elseif(function_exists('iconv'))
-            {
-                $output = @iconv('utf-8', $this->post->encode . '//TRANSLIT', $output);
-            }
-        }
+        if($this->post->encode != "utf-8") $output = helper::convertEncoding($output, 'utf-8', $this->post->encode . '//TRANSLIT');
 
         $this->sendDownHeader($this->post->fileName, 'csv', $output);
     }
diff --git a/module/file/model.php b/module/file/model.php
index 3acfa16612..6ba159e842 100644
--- a/module/file/model.php
+++ b/module/file/model.php
@@ -488,14 +488,7 @@ class fileModel extends model
         {
             if($uploadFile['folder']) continue;
             $fileName = $uploadFile['filename'];
-            if(function_exists('iconv'))
-            {
-                $fileName = iconv('gbk', 'utf-8//TRANSLIT', $fileName);
-            }
-            elseif(function_exists('mb_convert_encoding'))
-            {
-                $fileName = mb_convert_encoding($fileName, 'utf-8', 'gbk');
-            }
+            $fileName = helper::convertEncoding($fileName, 'gbk', 'utf-8//TRANSLIT');
             if(($pos = strrpos($fileName, '/')) !== false) $fileName = substr($fileName, $pos + 1);
 
             $file = array();
diff --git a/module/git/model.php b/module/git/model.php
index bf6005d83d..6d42a619db 100644
--- a/module/git/model.php
+++ b/module/git/model.php
@@ -397,7 +397,7 @@ class gitModel extends model
         foreach($encodings as $encoding)
         {
             if($encoding == 'utf-8') continue;
-            $result = @mb_convert_encoding($comment, 'utf-8', $encoding);
+            $result = helper::convertEncoding($comment, $encoding, 'utf-8');
             if($result) return $result;
         }
 
diff --git a/module/testcase/control.php b/module/testcase/control.php
index a773edc55e..f19224f051 100644
--- a/module/testcase/control.php
+++ b/module/testcase/control.php
@@ -1074,18 +1074,7 @@ class testcase extends control
             {
                 $fc     = file_get_contents($fileName);
                 $encode = $this->post->encode != "utf-8" ? $this->post->encode : 'gbk';
-                if(function_exists('mb_convert_encoding'))
-                {
-                    $fc = @mb_convert_encoding($fc, 'utf-8', $encode);
-                }
-                elseif(function_exists('iconv'))
-                {
-                    $fc = @iconv($encode, 'utf-8', $fc);
-                }
-                else
-                {
-                    die(js::alert($this->lang->testcase->noFunction));
-                }
+                $fc     = helper::convertEncoding($fc, $encode, 'utf-8');
                 file_put_contents($fileName, $fc);
 
                 $rows      = $this->file->parseCSV($fileName);