1.table自带功能

html
<table class="parent">
    <tr>
      <td class="child">
      垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中
      </td>
    </tr>
  </table>
  
css
.parent{
  border: 1px solid red;
  height: 200px;
}

.child{
  border: 1px solid green;
}

2.100% 高度的 afrer before 加上 inline block

html
<div class="parent">
    <span class=before></span><div class="child">
      
      垂直居中垂直居中垂直居中垂直居中
      
    </div><span class=after></span>
  </div>
  
css
.parent{
  border: 3px solid red;
  height: 200px;
  text-align: center;
}

.child{
  border: 3px solid black;
  display: inline-block;
  width: 300px;
  vertical-align: middle;
}

.parent .before{
  outline: 3px solid red;
  display: inline-block;
  height: 100%;
  vertical-align: middle;
}
.parent .after{
  outline: 3px solid red;
  display: inline-block;
  height: 100%;
  vertical-align: middle;
}

3.div 装成 table

html
<div class="parent">
    <div class="child">
      垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中
    </div>
  </div>
  
css
.parent{
  height: 200px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  width: 300px;
  position: absolute;
  top: 50%;
  left: 50%;
  margin-left: -150px;
  height: 100px;
  margin-top: -50px;
}

4.margin-top -50%

html
<div class="parent">
    <div class="child">
      垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中
    </div>
  </div>
  
css
.parent{
  height: 200px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  width: 300px;
  position: absolute;
  top: 50%;
  left: 50%;
  margin-left: -150px;
  height: 100px;
  margin-top: -50px;
}

5.translate -50%

html
 <div class="parent">
    <div class="child">
      垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中
    </div>
  </div>
  
css
.parent{
  height: 200px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%,-50%);
}

6.absolute margin auto

html
<div class="parent">
    <div class="child">
      垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中
    </div>
  </div>
  
css
.parent{
  height: 200px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  position: absolute;
  width: 300px;
  height: 100px;
  margin: auto;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}

7.flex

html
<div class="parent">
    <div class="child">
      垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中垂直居中
    </div>
  </div>
  
css
.parent{
  height: 200px;
  border: 3px solid red;
  
  display: flex;
  justify-content: center;
  align-items: center;
}
.child{
  border: 3px solid green;
  width: 300px;
}