Below are some data of China search market share in 2018:
Baidu is still the biggest search engine in China. Sogou increased further (14.89% search engine market share in 2019). This is benefited by its cooperation with browsers (such as QQ browser), websites (such as Zhihu) and App (such as WeChat).
Sogou achieved more market share on desktop (38.13%). So if you target desktop traffic, Sogou is more important in your marketing plan.
Compared to 2019, Baidu achieved more market share on mobile end. Sogou, replaced Shemma (owned by Alibaba) is the second search engine on mobile, but less than 7%.