在felx布局中可以使用gap来设置元素之间的间隔；

.box{
     width: 800px;
     height: auto;
     border: 1px solid green;
     display: flex;
     flex-wrap: wrap;
     gap: 100px;
} 
       
.inner{
     width: 200px;
     height: 200px;
     background-color: skyblue;
}

<div class="box">
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
</div>

 效果：