Although there is no published list of sites and services blocked in China, internet traffic can be blocked based on DNS, IP address, URL keywords, and actual site content. Some of this is maintained in blacklists, while real-time content monitoring is also employed, both automated and manual. Based on China laws, any suspected illegal content entering the country from abroad is kept from users via connection resets and black-hole loops.
If your site is blocked, there is no recourse to have it un-blocked. Your best solution is to get an ICP Filing with China’s Ministry of Industry and Information Technology (MIIT), which all sites in China are legally required to have. After this approval, your site will be available to all Chinese users.