<script src="Scripts/jquery-1.4.1.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function () {
Test("txt1");
});
function Test(id) {
alert($("#" + id).val()); // alert($(id).val(););
}
</script>
<input type="text" name="name" id="txt1" value="我是txt1的value," />