@media only screen and (min-width: 320px) and (max-width: 479px){
    html {
        font-size: 42.67px !important;
    }
}
@media only screen and (min-width: 480px) and (max-width: 639px){
    html {
        font-size: 64px !important;
    }
}
@media only screen and (min-width: 640px) and (max-width: 749px){
    html {
        font-size: 85.34px !important;
    }
}
@media only screen and (min-width: 750px) and (max-width: 959px){
    html {
        font-size: 100px !important;
    }
}
@media only screen and (min-width: 960px) and (max-width: 1241px){
    html {
        font-size: 128px !important;
    }
}
@media only screen and (min-width: 1242px){
    html {
        font-size: 165.6px !important;
    }
}

（zepto / jQuery）（750px设计图的1rem = 100px）
function setFont() {
    let window_width = window.innerWidth;
    let font_size = parseFloat(window_width / 3.75);
    $('html').css('font-size', font_size);
}
 
$(window).on('resize', function () {
    setFont();
});