借鉴了一下网上思路， 写个了代码， 经测试， OK, 如下：
<html>
<body >
<div style="position:relative;">
<span style="margin-left:100px;width:18px;overflow:hidden;">
<select id="xxx" style="width:118px;margin-left:-100px" οnchange="this.parentNode.nextSibling.value=this.value">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
</span>
<input id="yyy" style="width:100px;position:absolute;left:0px;">
</div>
<br />
<button onClick="test()">test </button>
<script>
function test()
{
var x = document.getElementById("yyy");
alert(x.value);
}
</script>
</body>
</html>