/*滚动条样式*/

        .innerbox::-webkit-scrollbar {/*滚动条整体样式*/

            width: 4px;     /*高宽分别对应横竖滚动条的尺寸*/

            height: 4px;

        }

        .innerbox::-webkit-scrollbar-thumb {/*滚动条里面小方块*/

            border-radius: 5px;

            -webkit-box-shadow: inset 0 0 5px rgba(0,0,0,0.2);

            background: rgba(0,0,0,0.2);

        }

        .innerbox::-webkit-scrollbar-track {/*滚动条里面轨道*/

            -webkit-box-shadow: inset 0 0 5px rgba(0,0,0,0.2);

            border-radius:;

            background: rgba(0,0,0,0.1);

        }

<div class="inner">

    <div class="innerbox">

        <p style="height:200px;">这是内容111</p>

        <p style="height:400px;">这里是内容222</p>

        <p>这里是内容333</p>

    </div>

</div>