<!--
ID_Class1 大类ID
Name_Class1 大类名称

ID_Class2 小类ID
Class1ID 所属大类ID
Name_Class2小类名称

-->
<select name="Class1" onChange="javascript:change_select(this.options[this.selectedIndex].value)">
<option value="0">选择分类</option>
<%
Set rs =Server.CreateObject("ADODB.RecordSet")
sql="select * from DH_Class1"
rs.open sql,conn,1,1
For i = 1 To rs.RecordCount%>
<option value="<%=rs("ID_Class1")%>"><%=rs("Name_Class1")%></option>
<%rs.MoveNext
Next
rs.Close
sql="select * from DH_Class2"
rs.open sql,conn,1,1
%>
</select>
<select name="Class2">
<option value="0">选择小类别</option>
</select>
<script language = "javascript">
arrSelect=new Array();
arrSelect[0] = new Array("选择分类",0,0)
<%
For i = 1 To rs.RecordCount
%>
arrSelect[<%= i %>]=new Array("<%= rs("Name_Class2") %>","<%= rs("Class1ID") %>","<%= rs("ID_Class2") %>");
<%
rs.MoveNext
Next
rs.Close
Set rs=nothing
%>
function change_select(selvalue)
{
document.all.Class2.length=0;
var i;
for(i=0;i<arrSelect.length;i++)
{
if(arrSelect[1]==selvalue)
{
var newOption=new Option(arrSelect[0],arrSelect[2]);
document.all.Class2.add(newOption);
}
}
}
</script>

==运行结果如下：===
<!-- group 的下拉列表-->
<select name="sltGroupID"
onChange="change_select(this.options[this.selectedIndex].value)">
<option selected value="0">用户组……</option>
<option value="1">直属机构</option>
<option value="2">办事处</option>
<option value="3">技术部</option>
</select>
<!-- user 的下拉列表-->
<select name="sltUserID">
<option selected value="0">用户……</option>
</select>
<script language = "javascript">
//读入 rsUser的数据
arrSelect=new Array();
arrSelect[0]=new Array("用户……",0,0)
arrSelect[1]=new Array("总经办","1","1");
arrSelect[2]=new Array("网络中心","1","15");
arrSelect[3]=new Array("公共平台","1","4");
arrSelect[4]=new Array("售后部","1","20");
arrSelect[5]=new Array("广州","2","24");
arrSelect[6]=new Array("上海","2","23");
arrSelect[7]=new Array("售前支持","3","8");
arrSelect[8]=new Array("研发中心","3","9");
//更新 user 下拉列表的函数
function change_select(selvalue)
{
document.all.sltUserID.length=0;
var i;
for(i=0;i<arrSelect.length;i++)
{
if(arrSelect[1]==selvalue)
{
var newOption=new Option(arrSelect[0],arrSelect[2]);
document.all.sltUserID.add(newOption);
}
}
}
</script>