Currently, the Nintendo Switch is not available in China, though the company has stated an interest in launching the console officially in the market if it can. While the Switch does support the Chinese language, and is even available for sale in Hong Kong, the mainland market remains inaccessible to it.
That said, Nintendo is probably very close to getting government approval to launch the system there. According to a report by The Wall Street Journal, Nintendo has partnered with Tencent, who have filed a report on Nintendo’s behalf, and the Switch was approved during the approval window of March 5 to Match 18, 2019. Beyond the confirmation of this filing, neither Nintendo nor Tencent have issued any official comment, nor is a launch actually announced yet, though it’s unlikely that either company would have bothered to file for an approval at all if that weren’t going to happen sooner rather than later.
Presuming Nintendo and Tencent do sell the Switch in China, the addressable market for the console would become far larger, leading to potentially higher sales—though as of right now, China has yet to be a meaningful factor in worldwide console sales. If it does happen though, hopefully Nintendo gets Nintendo Switch Online running there first.