ul li {

            position:relative;

            display: table;

            width:3rem;

            height:3rem;

            background:url('image/defaultBg.jpg') 0 0/100% 100% no-repeat; float:left;

            margin-bottom:0.2rem;

            text-align:center;

            box-shadow: 0 0 0.2rem #888;

            transition: all 0.3s linear;

            transform-origin: 0 0;

            transform-style: preserve-3d;

            color:#b21e23;

            font-weight:bold;font-size: 18px;

            border:1px solid #b21e23;

            overflow: hidden;

        }

li .selects_item{

            position:absolute;

            top:50%;

            left:50%;

            display:table-cell;

            vertical-align:middle;

            height:1.3rem;

        }

lit .selects_item p{

            position:relative;

            top:-50%;

            left:-50%;

            width:3rem;

            margin:0 auto;

        }

<div>

        <ul>

            <li>

                <div class="selects_item">

                     <p>我是多行文本</p>

                     <p>我不确定行数，单行或多行</p>

                </div>

            </li>

        </ul>

    </div>