<input id="admin1" type="radio" name="admin" value="0">
<input id="admin2" type="radio" name="admin" value="1">

设置radio的值
if(ret["is_sys_admin"] == "0"){
        $("#admin2").attr("checked","checked");
        $("#admin1").removeAttr("checked");
    }else {
        $("#admin1").attr("checked","checked");
        $("#admin2").removeAttr("checked");
    }

获取radio的值
var isadmin = $("input[name='admin']:checked").val();