不知是否如你所需:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script type="text/javascript">
window.attachEvent("onload", function () {
var btnid= '<%= btn.ClientID %>';
document.getElementById(btnid).disabled=true;
});
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:Button runat="server" ID="btn" Text="点击我" />
</form>
</body>
</html>