Through constructing the social integration assessment index system of migrant population from four dimensions, i. e. , politics, economy, public service, and psychological culture, on the basis of the literature, this research examines social integration of migrant population in 50 cities of major population inflows across the country. The evaluation results show that the overall social integration of the migrant population in the 50 cities is not high, and there are significant differences among different dimensions. The integration level ranking from high to low is the dimension of public service, politics, economy, and psychological culture. The level of social integration of migrants also varies across different regions and types of cities. It is recommended that the reform of the household registration system should be continued to break the institutional barriers of the social integration of the migrant population; education and employment training should be strengthened to improve the capacity of the migrant population in order to promote their integration; basic public services should be provided for the migrant population in order to reduce their dependence on the land and their traditional social relations. According to the laws and wishes of population mobility, the urbanization strategy will be adjusted.