选择器错了
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<table><tr><td>
<select name="authorityId1"
size="5" multiple="multiple" class="authorityId1" style="width: 120px;"></select>
</td>
<td align="center">
<button class="left" type="button">&gt;</button> <br /> 
<button class="right" type="button">&lt;</button>
</td>
<td valign="top">
                               <select name="authorityId" size="5"
multiple="multiple" class="authorityId" style="width: 120px;">
<option value="1" >老师</option>
<option value="2" >课程阶段</option>
                                <option value="3" >综合技能点</option>
                                <option value="4" >作业附件类型</option>
                                <option value="5" >帐号</option>
</select>
</td></tr></table>
<script>
    $("button.left").click(function () {
        var oSelect1 = $("select.authorityId1");
        var oSelect = $("select.authorityId");
        oSelect1.find("option:selected").appendTo(oSelect);///////
    });    $("button.right").click(function () {
        var oSelect1 = $("select.authorityId1");
        var oSelect = $("select.authorityId");
        oSelect.find("option:selected").appendTo(oSelect1);/////
    });
</script>