<html> <head> <!--禁止页面缓存-->
<meta http-equiv="content-type" content="text/html;charset=utf-8" /> <META HTTP-EQUIV="Pragma" CONTENT="no-cache"> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> <META HTTP-EQUIV="Expires" CONTENT="0"> </head> <select id="ss"> <option >aa0</option> <option >aa1</option> <option >aa2</option> <option >aa3</option> </select> <body> <script > var ss = document.getElementById('ss'); ss[3].selected = true;//选中 </script> </html>