其实很简单，在你的项目根目录下新建一个vercel.json

{
  "headers": [
    {
      "source": "/(.*)",
      "headers": [
        { "key": "Access-Control-Allow-Credentials", "value": "true" },
        { "key": "Access-Control-Allow-Origin", "value": "*" },
        { "key": "Access-Control-Allow-Methods", "value": "GET,OPTIONS,PATCH,DELETE,POST,PUT" },
        { "key": "Access-Control-Allow-Headers", "value": "X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Api-Version" }
      ]
    }
  ]
}

source 就是允许跨域的路径，我这边设置的是所有路径，即在这个网站上任何路径跨域都是可以的