<!DOCTYPE HTML> <html lang="en-US"> <head> <meta charset="UTF-8"> <title>test</title> <style> .btn { width: 100px; text-align: center; height: 50px; line-height: 50px; background: #000; color: #fff; position: relative; } .btn:after { position: absolute; content: ''; ------------主要是为了撑开容器div width: 30px; height: 30px; background: #fff; top: 10px; right: -15px; border-radius: 100%; } </style> </head> <body> <div class="btn"> button </div> </body> </html>