China has always been associated with "mystery", more so with its internet world. There are Chinese internet giants that are known to the westerners, but practically many people are not aware of how the internet society looks like in China.
Not mention about SEO in China.
Due to the government regulation, all the public internet services must filter their content before being published, and users must sign up with their mobile phone and the ones who want to publish content must upload their identification. It gives a HUGE barrier for foreigners to get to the Chinese internet ecosystem and this is, I think, intentional.
I'm going to offer you some resources that you can build your backlinks in China for free, and it not only adds your presence in Chinese search engine but in Google as well.
1. Jian Shu (literally means "Simple Book")
Jianshu is a site for sharing articles, and most importantly, it's by far the only online article platform that allows hyperlinks in the article and in the comment section.
Please feel free to leave your URL at the comment section of my article:
2. Sina blog
Leave your url in Sina blog comment section will not become a hyperlink, but the text itself is good enough for search purpose. System will remove anything starting with http:// or https://, so do not include them.
3. Lofter blog
Lofter is another my favorite online platform for links, in the following article link, just scroll to the bottom and you will see comment section. URL will be translated into hyperlinks.
4. Zhihu (literally means: To know)
Zhihu is the Quora of China, they have a article section and all the url in the comments are hyperlinked.
You can leave your back link in my Zhihu article, at the bottom of the page