The research on urban size distribution is beneficial to correctly recognize current city number and size and provides theoretical basis for making urban development policies. Taking total number of population at the end of a year in the area administered by a city as calculation index, this paper indicates that the Pareto Coefficient of China’s city size distribution is 1.2169 in 2008, which is fit for rank-size law, however, Pareto Coefficient of China’s city size distribution is 1.0061 by taking non-agricultural population in the area administered by a city as calculation index, which shows that the homogeneous degree of city size distribution decreases. Except very few situations, Pareto Coefficient of city size distribution of the provinces and municipalities with higher economic development level is relatively higher but is lower in the provinces and municipality with lower economic development level. Compared with provincial and municipal level, the city size distribution at national level is more even.