http://blog.csdn.net/lee576/archive/2008/11/24/3362512.aspx
html中的2个普通select
<select id="province"></select>
<select id="city"></select>
先倒入2个插件：
<script language="javascript" type="text/javascript" src="js/jQuery.FillOptions.js"></script>
<script language="javascript" type="text/javascript" src="js/jQuery.CascadingSelect.js"></script>
$("#province").FillOptions(
"flexGridServlet.do?action=getProvince",
{
datatype:"json",
textfield:"province",
valuefiled:"provinceID