Taking Shanghai, a city with an urbanization rate of over 80% in terms of its permanent resident population, as an example, the paper constructs a comprehensive evaluation system from four perspectives of population, economic development, life style and built environment, and uses the entropy method to measure the urbanization process of Shanghai from 2005 to 2016. Comparatively speaking, both aspects of life style and built environment impose more significant influences on Shanghai's urbanization in recent years. As Shanghai's urbanization entering the maturity stage, the quantitative analysis of multiple factors further reveals that the urban development in such a stage relies on the promotion of urban comprehensive circumstance more than on the economic development. As China's urbanization is still in the accelerating stage as a whole, Shanghai's experience of the maturity stage of urbanization is supposed to shed some light on the whole country's urbanization in future.