html
<div class="container">
        <div class="content">好的</div>
    
</div>


css
.container {
            position:relative;
            width:200px;
            height:100px;
            background:red;
            margin:10px;
            padding:10px;
            border:5px solid #000;

        }
        .content {
            text-align:center;
             width:100%; 
             position:absolute;
            left:30px;
            right:30px; 
            background:blue;
        }