方法1（jquery）：animate();
方法2（css）：transition;
<!DOCTYPE html><html><head><meta charset="utf-8" /><title></title> <style type="text/css"> * { margin: 0; padding: 0; } .father { overflow: hidden; position: relative; width: 200px; height: 200px; background: #fff; border: 1px solid #000; margin: 0 auto; } .son { position: absolute; top: -100%; left: 0; width: 200px; height: 200px; background: rgba(0,0,0,.5); color: #fff; } </style> <style type="text/css"> .father1 { overflow: hidden; position: relative; width: 200px; height: 200px; background: #fff; border: 1px solid #000; margin: 0 auto; } .son1 { position: absolute; top: -100%; left: 0; width: 200px; height: 200px; background: rgba(0,0,0,.5); color: #fff; transition: top 1s; } .father1:hover .son1 { top: 0%; } </style> </head> <body> <!-- jq方法 --> <div class="father"> I am Father <div class="son">I am Son</div> </div> <script type="text/javascript" src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script> <script type="text/javascript"> $('.father').mouseover(function () { $(this).find('.son').stop() $(this).find('.son').animate({'top': '0%'}, 'slow') }).mouseout(function() { $(this).find('.son').stop() $(this).find('.son').animate({'top': '-100%'}, 'slow') }) </script> <!-- css方法 --> <div class="father1"> I am Father1 <div class="son1">I am Son1</div> </div> </html>