SOURCE

<div class="container">
    <div class="content">1</div>
    <div class="content">2</div>
    <div class="content">3</div>
    <div class="content">4</div>
    <div class="content">5</div>
    <div class="content">6</div>
    <div class="content">7</div>
    <div class="content">8</div>
    <div class="content">9</div>
    <div class="content">10</div>
    <!-- 解决最后一行对齐问题 -->
    <div class="empty"></div>
    <div class="empty"></div>
    <div class="empty"></div>
    <div class="empty"></div>
    <div class="empty"></div>
    <div class="empty"></div>    
</div>

.container {
    background-color: paleturquoise;
    height: 300px;
    display: flex;
    flex-wrap: wrap;
    width: 500px;
}
.content {
    height:30px;
    /* width:80px; */
    flex:1;
    min-width:80px;
    background-color: pink;
    margin-right:3px;
}
/* 解决最后一行对齐问题 */
.empty {
    height:0px;
    /* width:80px; */
    flex:1;
    min-width:80px;
    background-color: pink;
    margin-right:3px;
}