网上三级菜单多是多但是代码都比较烦，我这个应该说还是比较直观的：
'肯定先要连接数据库了，不用说了
'数据库结构
'类别1表名称：a 字段：ID,Name 说明：ID为主键是类别1的ID值，Name为类别1的名称
'类别2表名称：aa 字段：ID,aID,Name 说明：ID为主键是类别2的ID值，aID为所属类别1的ID值，Name为类别2的名称
'类别3表名称：aaa 字段：ID,aID,aaID,Name 说明：ID为主键是类别3的ID值，aID为所属类别1的ID值，aaID为所属类别2的ID值，Name为类别3的名称
=====test1.asp 你可以测试下，接收到的都是类别的ID值====
<%
response.write"1:"&Request.form("s1")&"<BR>"
response.write"2:"&Request.form("s2")&"<BR>"
response.write"3:"&Request.form("s3")&"<BR>"
%>
<!-- 三级联动菜单 开始 -->
<script language="JavaScript">
<!--
<%
'二级数据保存到数组
Dim count2,rsClass2,sqlClass2
set rsClass2=server.createobject("adodb.recordset")
sqlClass2="select * from aa"
rsClass2.open sqlClass2,conn,1,1
%>
var subval2 = new Array();
//数组结构：一级根值,二级根值,二级显示值
<%
count2 = 0
do while not rsClass2.eof
%>
subval2[<%=count2%>] = new Array('<%=rsClass2("aID")%>','<%=rsClass2("ID")%>','<%=rsClass2("Name")%>')
<%
count2 = count2 + 1
rsClass2.movenext
loop
rsClass2.close
%>
<%
'三级数据保存到数组
Dim count3,rsClass3,sqlClass3
set rsClass3=server.createobject("adodb.recordset")
sqlClass3="select * from aaa"
rsClass3.open sqlClass3,conn,1,1
%>
var subval3 = new Array();
//数组结构：二级根值,三级根值,三级显示值
<%
count3 = 0
do while not rsClass3.eof
%>
subval3[<%=count3%>] = new Array('<%=rsClass3("aaID")%>','<%=rsClass3("ID")%>','<%=rsClass3("Name")%>')
<%
count3 = count3 + 1
rsClass3.movenext
loop
rsClass3.close
%>
function changeselect1(locationid)
{
document.form1.s2.length = 0;
document.form1.s2.options[0] = new Option('==请选择类别==','');
document.form1.s3.length = 0;
document.form1.s3.options[0] = new Option('==请选择专题==','');
for (i=0; i<subval2.length; i++)
{
if (subval2[i][0] == locationid)
{document.form1.s2.options[document.form1.s2.length] = new Option(subval2[i][2],subval2[i][1]);}
}
}
function changeselect2(locationid)
{
document.form1.s3.length = 0;
document.form1.s3.options[0] = new Option('==请选择专题==','');
for (i=0; i<subval3.length; i++)
{
if (subval3[i][0] == locationid)
{document.form1.s3.options[document.form1.s3.length] = new Option(subval3[i][2],subval3[i][1]);}
}
}
//-->
</script>
<form name="form1" method="post" action="test1.asp">
三级联动：
<%
Dim count1,rsClass1,sqlClass1
set rsClass1=server.createobject("adodb.recordset")
sqlClass1="select * from a"
rsClass1.open sqlClass1,conn,1,1
%>
<select name="s1" onChange="changeselect1(this.value)">
<option>==请选择频道==</option>
<%
count1 = 0
do while not rsClass1.eof
response.write"<option value="&rsClass1("ID")&">"&rsClass1("Name")&"</option>"
count1 = count1 + 1
rsClass1.movenext
loop
rsClass1.close
%>
</select>
<select name="s2" onChange="changeselect2(this.value)">
<option>==请选择类别==</option>
</select>
<select name="s3">
<option>==请选择专题==</option>
</select>
<input type="submit" name="Submit" value="提交"></form>
<!-- 三级联动菜单 结束 -->