代码如下，以便自己以后方便查阅：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>菜单二级联动效果</title>
</head>
<body>
<script language="JavaScript" type="text/javascript">
/*var city=[
["北京","天津","上海","重庆"],
["南京","苏州","南通","常州"],
["福州","福安","龙岩","南平"],
["广州","潮阳","潮州","澄海"],
["兰州","白银","定西","敦煌"]
];*/
//或者
var city = new Array;
city[0] = Array("北京","天津","上海","重庆");
city[1] = Array("南京","苏州","南通","常州");
city[2] = Array("福州","福安","龙岩","南平");
city[3] = Array("广州","潮阳","潮州","澄海");
city[4] = Array("兰州","白银","定西","敦煌");
function getCity(){
var sltProvince=document.getElementById("province");
var sltCity=document.getElementById("city");
var provinceCity=city[sltProvince.selectedIndex-1];
sltCity.length=1;
for(var i=0;i<provinceCity.length;i++){
sltCity[i+1]=new Option(provinceCity[i],provinceCity[i]);
}
} </script>
<form action="#" name="theForm">
<select name="province" id="province" onchange="getCity()">
<option value="0">请选择所在省份</option>
<option value="直辖市">直辖市</option>
<option value="江苏省">江苏省</option>
<option value="福建省">福建省</option>
<option value="广东省">广东省</option>
<option value="甘肃省">甘肃省</option>
</select>
<select id="city" name="city">
<option value="0">请选择所在城市</option>
</select>
</form>
</body>
</html>
效果如下：