引入如下js内容（按照750px设计稿宽度配置）：
<script type="text/javascript">
(function (doc, win) {
let docEl = doc.documentElement
let resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'
let recalc = function () {
let clientWidth = docEl.clientWidth
if (!clientWidth) return
if (clientWidth >= 750) {
docEl.style.fontSize = '100px'
} else {
docEl.style.fontSize = 100 * (clientWidth / 750) + 'px'
}
}
if (!doc.addEventListener) return
win.addEventListener(resizeEvt, recalc, false)
recalc()
doc.addEventListener('DOMContentLoaded', recalc, false)
})(document, window)
</script>
