全局引入

(function(doc, win) {
    const docEl = doc.documentElement,
        resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'
        const setFont = function() {
            let clientWidth = docEl.clientWidth;
            if (!clientWidth) return;
            if (clientWidth >= 750) {
                docEl.style.fontSize = '16px';
            } else {
                docEl.style.fontSize = 16 * (clientWidth / 750) + 'px';
            }
        };

    doc.addEventListener('DOMContentLoaded', setFont, false)
    win.addEventListener(resizeEvt, setFont, false)
    win.addEventListener('load', setFont, false)
})(document, window);

以1rem为16px为准设置html标签fontSize，蓝湖则设置如下图！搞定😊