实现没有什么技术含量，有兴趣的朋友往下看。
页面上需要一个放置新增控件的控件：<span id="moreFile"></span>，添加控件的按钮：<input type="button" id="bt1" onclick="addFile()" value="更多文件" />
然后，就是两个JS：
<script type="text/javascript">
function addFile()
{
var mf = document.getElementById("moreFile");
var html = "<span style='height:30px'><input type='file' name='FileSelect' style='width:470px'/> ";
html += "<input type='button' value='删除' class='btn1' onclick='deleteFile()'/></span><br/>";
mf.innerHTML += html;
}
function deleteFile()
{
var mf = document.getElementById("moreFile").innerHTML;
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
document.getElementById("moreFile").innerHTML = mf;
}
</script>
function addFile()
{
var mf = document.getElementById("moreFile");
var html = "<span style='height:30px'><input type='file' name='FileSelect' style='width:470px'/> ";
html += "<input type='button' value='删除' class='btn1' onclick='deleteFile()'/></span><br/>";
mf.innerHTML += html;
}
function deleteFile()
{
var mf = document.getElementById("moreFile").innerHTML;
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
mf = mf.substring(0, mf.lastIndexOf("<"));
document.getElementById("moreFile").innerHTML = mf;
}
</script>
利用了innerHTML属性。效果图：