//动态改变少数民族的值
function checkSelect(){
var ontion = document.getElementById("nations").value;
//alert("少数民族的值为:"+ontion);
var on = document.getElementById("na2").value=ontion;
//alert("赋值为:"+on);
}
<input id="na" type="radio" name="ysBaseInfo.nation" value="1" />汉族
<input id="na2" type="radio" name="ysBaseInfo.nation" value="0" />少数民族
<select id="nations" οnchange="checkSelect();" class="input_select1">
<option></option>
<option value="2">蒙古族</option>
<option value="3">回族</option>
<option value="4">藏族</option>
<option value="5">维吾尔族</option>
<option value="6">苗族</option>
<option value="7">彝族</option>
<option value="8">壮族</option>
</select>