方式一 float+ text-align:center
<div class="w clearfix tc mt10"> <el-button class="fll" type="primary" plain>刷新</el-button> <el-button type="primary" plain>全部展开</el-button> <el-button class="flr" type="primary" plain>全部收起</el-button> </div>
方式二 float+margin: 0 auto
方式三 padding+absolute+margin: 0 auto
原文：https://www.cnblogs.com/dianzan/p/13261800.html