может так?
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script>
$(function ()
{
$(document).ready(function(){
$("#select1 option").prop("selected", false).filter(":nth-child(1)").prop("selected", true);
});
})
</script>
</head>
<body>
<select id="select1" >
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</body>
</html>