
Social media platforms such as Facebook, Twitter, Instagram, Whatsapp, and others have been blocked by the great chinese firewall since 2009. If people can send digital transmissions unmonitored, then it can’t be approved. Gmail is blocked because the Chinese authorities doesn’t have access to the user data it demands.

Google refused to omit certain politically sensitive topics from search, and you can probably guess what those were. Because Google didn't go along with the Chinese authorities and their internet censorship on their platform, China put measures in place to block their services from the Chinese market in 2010. Anything hosted by Google is unavailable in mainland China. This includes things such as Google Docs, Google Sheets, Blogger, YouTube, and so on.

Yes, Gmail in China is blocked along with all Google services by the Great Chinese Firewall.
