*{
    margin: 0 auto;
    padding: 0;
}
@rem:75rem;
.webpage{
    width: 750/@rem;
    height: 1334/@rem;
    background: url(../image/背景图.png) no-repeat;
    background-size:cover ;
}

<!DOCTYPE html>

<html>
    <head>
        <meta charset="UTF-8">
        <title>姚辉乾</title>
        <link rel="stylesheet" href="css/index.css" />
            <script type="text/javascript" charset="utf-8">              
          (function () {
               var timer;
            changeFixedW();
              function changeFixedW(){
            var html = document.querySelector('html');
            var width = html.getBoundingClientRect().width;
            html.style.fontSize = width / 10 + 'px';
           }
            window.addEventListener('resize', function () {
                clearTimeout(timer);
                timer = setTimeout(changeFixedW, 300);
            }, false);
        })();
    </script>
    </head>
    <style>
        
    </style>
    <body>
        <section class="webpage">
            
        </section>
    </body>
</html>