先看演示效果

首先引入JS

<script type="text/javascript">
  document.getElementById("mcvideo").style.height =
    document.getElementById("mcvideo").scrollWidth * 0.65 + "px";
</script>

视频引入代码

<iframe
  id="mcvideo"
  src="https://player.bilibili.com/player.html?aid=969951173&page=1&high_quality=1"
  scrolling="no"
  border="0"
  frameborder="no"
  framespacing="0"
  allowfullscreen="true"
  width="100%"
>
</iframe>