效果展示

    <div class="father">
        <div class="damao"></div>
    </div>

绝对定位

        .father {
            position: relative;
            width: 500px;
            height: 400px;
            background-color: pink;
        }
        .damao {
            position: absolute;
            top: 0;
            right: 0;
            bottom: 0;
            left: 0;
            margin: auto;
            width: 150px;
            height: 150px;
            background-color: purple;
        }

绝对定位+负边距

        .father {
            position: relative;
            width: 500px;
            height: 400px;
            background-color: pink;
        }
        .damao {
            position: absolute;
            top: 50%;
            left: 50%;
            margin-top: -75px;
            margin-left: -75px;
            width: 150px;
            height: 150px;
            background-color: purple;
        }

绝对定位+transform

        .father {
            position: relative;
            width: 500px;
            height: 400px;
            background-color: pink;
        }
        .damao {
            position: absolute;
            top: 50%;
            left: 50%;
            width: 150px;
            height: 150px;
            transform: translate(-50%, -50%);
            background-color: purple;
        }

Grid网格实现

        .father {
            display: grid;
            place-items: center;
            width: 500px;
            height: 400px;
            background-color: pink;
        }
        .damao {
            width: 150px;
            height: 150px;
            background-color: purple;
        }

flex弹性布局

        .father {
            display: flex;
            justify-content: center;
            align-items: center;
            width: 500px;
            height: 400px;
            background-color: pink;
        }
        .damao {
            width: 150px;
            height: 150px;
            background-color: purple;
        }

表格布局

        .father {
            display: table-cell;
            width: 500px;
            height: 400px;
            text-align: center;
            vertical-align: middle;
            background-color: pink;
        }
        .damao {
            display: inline-block;
            width: 150px;
            height: 150px;
            background-color: purple;
        }