方法是对的，但不能会得这么细，可以将代码集合在一起：

div {

  width: 200px;

  height: 200px;

  background-color: orange;

  margin: 20px auto;

  border-radius: 100%;

  /*-webkit-transition-property: -webkit-border-radius;

  transition-property: border-radius;

  -webkit-transition-duration: 1s;

  transition-duration: 1s;

  -webkit-transition-timing-function:linear;

  transition-timing-function:linear;

  -webkit-transition-delay: .2s;

  transition-delay: .2s;*/

  -webkit-transition: border-radius 1s linear .2s;

  transition: border-radius 1s linear .2s;

}

div:hover {

  border-radius: 0px;

}