<script type="text/javascript">
function submitFrom(){
$("#idForm").submit();
};
</script>
</head>
<body>
<h1>文件上传演示</h1>
<iframe name="aa" style="display:none;"></iframe>
<form id="idForm" action="xxx" method="post" enctype="multipart/form-data" target="aa">
<input type="file" name="xls" onchange="submitFrom()">
</form>
</body>
原文：http://www.cnblogs.com/zjqblog/p/7468047.html