China GFW may block google fonts in some area, even fonts.googleapis.com has its own Beijin server. It's not 100% stable for us to use google fonts, after all, its named Google which is hated by the Chinese government.
Someone will choice to use Chinese native CDN provider, but they are not friendly for other countries' people.
This mirror serve google fonts by the CDN of Github Pages, help chinese guys to create global Web sites.
Replace {Font_Family} to your font family name:
<link href="https://fonts.joway.io/css/{Font_Family}.css" rel="stylesheet" />
->
<link href="https://fonts.joway.io/css/Open+Sans.css" rel="stylesheet" />Define the font family in your css:
.cls {
font-family: "Open Sans", sans-serif;
}