<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<div class="wrap">
<div class="left"><div style="height:700px"></div></div>
<div class="right">111111111</div>
</div>
</body>
</html>
.wrap{
width:100%;
height:400px;
border:1px solid red;
display:flex; /*flex布局*/
}
.left{
width:5%;
height:500px;
background:gray;
flex:none;
overflow-y: auto;
}
.right{
height:100%;
background:green;
flex:1; /*flex布局*/
}