用flex布局

<div id="box">
 <div class="item">1</div>
 <div class="item">2</div>
 <div class="item">3</div>
 <div class="item">4</div>
 <div class="item">5</div>
 </div>
#box{
   display: flex;
   display: -webkit-flex;
   border: 1px solid #0000FF;
   height: 200px;
   width: 400px;
   align-items:center;
   justify-content:center;
 }
 .item{
   width: 50px;
   height: 40px;
   border: 1px solid #00C1B3;
 }