Edit in JSFiddle

<div class="div1">
我是浮动元素
</div>
<div class="div2">
2
</div>

div{
  width:200px;
  height:200px;
  background:pink;
  margin:10px;
}
.div1{
  width:300px;
  height:300px;
  background:green;
  float:left;
}