diff --git a/users/templates/users/login.html b/users/templates/users/login.html
index f11c8803..25c46753 100644
--- a/users/templates/users/login.html
+++ b/users/templates/users/login.html
@@ -36,8 +36,8 @@
             {% if user.is_authenticated %}
             <a href="{% url 'common:home' %}" class="button">{% trans '前往我的主页' %}</a>
             {% elif allow_any_site %}
-            <form action="/users/connect">
-            <input type="search" name="domain" id="domain" placeholder="输入实例地址，例如mastodon.social" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false" />
+            <form action="/users/connect" onsubmit="return /^(([a-zA-Z0-9-])+\.)+([a-zA-Z0-9]{2,4})$/.test($('#domain').val())">
+            <input type="search" name="domain" id="domain" placeholder="实例地址，如mastodon.social (不含@)" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false" />
             <input type='submit' value="{% trans '授权登录' %}" />
             </form>
             {% else %}