<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script src="http://libs.baidu.com/jquery/1.7.2/jquery.min.js"></script>
<script>
$(function(){
var menu = $('.menu');
menu.hover(function(){
$(this).children('ul').show();
},function(){
$(this).children('ul').hide();
});
});
</script>
<style>
*{margin: 0;padding: 0;}
li{list-style: none;}
body{margin: 50px;}
.hide{display: none;}
.menu{cursor: pointer;}
</style>
</head>
<body>
<ul>
<li class="menuLevel1 menu">
<span>一级菜单</span>
<ul class="hide">
<li class="menuLevel2 menu">
<span>二级菜单</span>
<ul class="hide">
<li class="menuLevel3 menu">
<span>三级菜单</span>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</body>
</html>
