<div>
<select id="first" onchange="setSecond(this)">
<option value="en">en</option>
<option value="zh">zh</option>
</select>
</div>
<div>
<select id="second"></select>
</div>
<script>
function setSecond(obj){
var val = obj.value;
if(val == "en"){
var sec = document.getElementById('second');
sec.innerHTML = "<option>one</option><option>two</ption>";
}else{
var sec = document.getElementById('second');
sec.innerHTML = "<option>一</option><option>二</option>";
}
}
</script>