Cases study on urbanization has been done lots in the western countries, whereas such works are rare in China. In order to reach a well-understanding of urbanization, the authors choose two typical cities, Beijing and Shenzhen, to compare their urbanization process. Firstly, the authors analyse   the urbanization processes of Beijing and Shenzhen. Then a comparison is given. From the comparison the authors find out that the differences of these two cities lie in six aspects: the increase patterns of urbanization level, the relation between the UL and GDP per capita, the population structure, the industry transformation, the land-use patterns and the environment problems. Finally, the reason why the urbanization processes of these two cities have so many differences is explored. The authors believe that different reaction patterns of the policy and economics in Beijing and Shenzhen during the reforming and open period are the main reason.