<iframe id="iframeId" src="a.html"></iframe>
----------a.html页面--------
<html>
<head>
<title>test</title>
</head>
<body>
<form id="forId"><table><tr><td>我的高度</td></tr></table></form>
</body>
</html>
<script>
parent.document.getElementById("iframeId").height=$("#forId").height();
</script>