子绝父相,定位到大盒子的宽高一半的位置,再用transform: translate向左向上移动自己宽高的一半
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.father{
width: 600px;
height: 600px;
background-color: orangered;
position: relative;
}
.son{
width: 300px;
height: 200px;
background-color: lawngreen;
position: absolute;
top: 50%;
left: 50%;
/*用transform向左(上)平移它自己宽度(高度)的50%,也就达到居中效果了*/
transform: translate(-50%,-50%);
}
</style>
</head>
<body>
<div class="father">
<div class="son"></div>
</div>
</body>
</html>
转自:https://blog.youkuaiyun.com/sleepwalker_1992/article/details/80656170