diff --git a/common.php b/common.php
index 401a165..f2bbb63 100644
--- a/common.php
+++ b/common.php
@@ -12,6 +12,7 @@ $Base64Env = [
     'background',
     'diskname',
     //'disableShowThumb',
+    //'disableChangeTheme',
     //'disktag',
     //'downloadencrypt',
     //'function_name', // used in heroku.
@@ -53,6 +54,7 @@ $CommonEnv = [
     'background',
     'disktag',
     'disableShowThumb',
+    'disableChangeTheme',
     'function_name', // used in heroku.
     'hideFunctionalityFile',
     'timezone',
@@ -76,6 +78,7 @@ $ShowedCommonEnv = [
     'background',
     //'disktag',
     'disableShowThumb',
+    'disableChangeTheme',
     //'function_name', // used in heroku.
     'hideFunctionalityFile',
     'timezone',
@@ -2650,19 +2653,17 @@ function render_list($path = '', $files = '')
         $html = str_replace('<!--FootStr-->', date("Y-m-d H:i:s")." ".getconstStr('Week')[date("w")]." ".$_SERVER['REMOTE_ADDR'].' Runningtime:'.$exetime.'s Mem:'.size_format(memory_get_usage()), $html);
     }
 
-    $theme_arr = scandir('theme');
-    $html .= '
+    if ($_SERVER['admin']||!getConfig('disableChangeTheme')) {
+        $theme_arr = scandir('theme');
+        $html .= '
 <div style="position: fixed;right: 10px;bottom: 10px;/*color: rgba(247,247,249,0);*/">
     <select name="theme" onchange="changetheme(this.options[this.options.selectedIndex].value)">
         <option value="">'.getconstStr('Theme').'</option>';
-    foreach ($theme_arr as $v1) {
-        if ($v1!='.' && $v1!='..') $html .= '
+        foreach ($theme_arr as $v1) {
+            if ($v1!='.' && $v1!='..') $html .= '
         <option value="'.$v1.'" '.($v1==$theme?'selected="selected"':'').'>'.$v1.'</option>';
-    }
-    //$tmp = getConfig('customTheme');
-    //if ($tmp!='') $html .= '
-    //    <option value="" '.($tmp==$theme?'selected="selected"':'').'>customTheme</option>';
-    $html .= '
+        }
+        $html .= '
     </select>
 </div>
 <script type="text/javascript">
@@ -2675,6 +2676,7 @@ function render_list($path = '', $files = '')
         location.href = location.href;
     }
 </script>';
+    }
 
     $html = $authinfo . $html;
     if (isset($_SERVER['Set-Cookie'])) return output($html, $statusCode, [ 'Set-Cookie' => $_SERVER['Set-Cookie'], 'Content-Type' => 'text/html' ]);