Poverty, crime rates increase and decrease in social security are often considered as “Urban Disease” during the process of urbanization and large amount of migrants’ influx into cities. With empirical studies in Shanghai, the authors try to analyze the relations between migrants’ absolute and relative congregation and the impacts to urban safety. The authors build a Public Safety Index (PSI) to measure the urban safety, make descriptive mapping of urban safety in Metropolis Shanghai from 2000 to 2010, and illustrate main reasons on urban safety. The empirical evidences show that although the correlation between population congregation and urban safety is significant, while controlled related variables, we could see non-hukou immigrants congregation actually has no significant influence to urban safety, and what really matters are the population’s age structure, educational level, marriage and family status, community-building and environment, economic development and labor market situation, and etc. Therefore, the authors suggest that the local authority should take migratory inclusive policies, which puts more emphasis on improving education, providing employment, enhancing community-building and community facilities construction, and so on, instead of carrying out strict population control policies to achieve the target of urban safety and immigrant development.