1.添加相应的script链接

jquery:

select2：

css:

js:

2.html页面添加select 

<div class="select1">

<select class="mySelect">

<option>西瓜</option>

<option>苹果</option>

<option>香蕉</option>

<option>菠萝</option>

<option>桃子</option>

</select>

</div>

3.在页面添加script

<script>

$(function(){

$('.mySelect').select2({

 placeholder: "--请选择--",

 allowClear: true

});

})

</script>