diff --git a/backend/application/admin/view/index/login.html b/backend/application/admin/view/index/login.html
index b2b0322..22c4de7 100644
--- a/backend/application/admin/view/index/login.html
+++ b/backend/application/admin/view/index/login.html
@@ -118,7 +118,7 @@
                             <div class="input-group-addon"><span class="glyphicon glyphicon-option-horizontal" aria-hidden="true"></span></div>
                             <input type="text" name="captcha" class="form-control" placeholder="{:__('Captcha')}" data-rule="{:__('Captcha')}:required;length({$Think.config.captcha.length})" autocomplete="off"/>
                             <span class="input-group-addon" style="padding:0;border:none;cursor:pointer;">
-                                    <img src="{:rtrim('__PUBLIC__', '/')}/index.php?s=/captcha" width="100" height="30" onclick="this.src = '{:rtrim('__PUBLIC__', '/')}/index.php?s=/captcha&r=' + Math.random();"/>
+                                    <img src="{:rtrim('__PUBLIC__', '/')}/index.php?s=/captcha" width="150" height="32" onclick="this.src = '{:rtrim('__PUBLIC__', '/')}/index.php?s=/captcha&r=' + Math.random();"/>
                             </span>
                         </div>
                         {/if}
diff --git a/backend/application/config.php b/backend/application/config.php
index 3869da7..f1989ac 100644
--- a/backend/application/config.php
+++ b/backend/application/config.php
@@ -246,9 +246,9 @@ return [
         // 验证码图片高度
         'imageH'   => 40,
         // 验证码图片宽度
-        'imageW'   => 130,
+        'imageW'   => 180,
         // 验证码位数
-        'length'   => 2,
+        'length'   => 4,
         // 验证成功后是否重置
         'reset'    => true
     ],