b.htm 中
<script language=javascript>
var bv;
function setBV(v) {
bv = v;
alert("我来SHOW:" + bv);
}
</script>
===========================================================
a.htm 中
<iframe name="cf" id="cf" src="b.htm" width=100 height=100></iframe>
<script language=javascript>
var ParentValue = "父窗口中的变量";
document.frames["cf"].onload = function() {
document.frames["cf"].setBV(ParentValue);
}
</script>