OECD calculates that China about 65% urbanized and has 17 megacities based on Functional urban area

Instead of just looking at cities' administrative borders or "statutory city population," OECD’s study takes into account surrounding“functional urban areas” (FUA), which may lie outside the administrative borders but are significant to the social and economic makeup of the city. A lot of this is the result of China’s complex “hukou” system, the registration license given to residents of a city, which limits the mobility of citizens from outside from residing inside administrative borders.

OECD functional urban area statistics are here

OECD figured china had 15 cities with at least 10 million people (defined as megacities) back in 2010 but now two more likely joined

UN Figures China is urbanizing faster than official estimates

If Functional urban areas are used to calculate urbanization then China was61.2% urbanized in 2010 and likely is about 65% urbanized now