var a = document.getElementById("mySelect");//mySelect是select 的Id
a.options[0].selected = true;
或者
document.getElementById("data_controll").options[0].selected = true;;
var a = document.getElementById("mySelect");//mySelect是select 的Id
a.options[0].selected = true;
或者
document.getElementById("data_controll").options[0].selected = true;;