In this study, we apply a stationarity test with a flexible Fourier function proposed by Enders and Lee Oxford Bulletin of Economics and Statistics, 74 (2012) 574-599 to test the convergence of China's urbanization. We find that our approximation has greater power to detect U-shaped and smooth breaks than the linear method if the urbanization is, in fact, a stationary non-linear process. It shows that the stationarity of the urbanization level varies across different regions where urbanization levels are convergent mainly in the middle- and low-income regions in China, while the high-income regions' urbanization is divergent. This, in turn, shows that most of the regions, especially high-income regions, have their own economic evolution rules due to the degree of openness in the economy and urbanization process. web URL: http://www.worldscientific.com/doi/abs/10.1142/S0217590815500587