The study explores the impacts of health insurance on the social integration of both rural migrants and urban migrants into cities in China. We construct a comprehensive integration index and employ the Quantile Regression method to examine the data collected from a nationwide survey by China's National Health Commission. We found that first, the degree of social integration of rural-urban migrants into cities is weaker than that for urban-urban migrants in varied dimensions. The gap between the two types of migrants' integration increases from lower quantiles to higher quantiles. Second, health insurance provided by the destination cities has improved the integration for both types of migrants. Its positive impact on social integration also accelerates in quantiles. Third, the accelerating positive impacts of health insurance on the rural-urban migrants' integration in quantiles are more significant than those for the urban-urban migrants. On the policy front, it is therefore important to raise the insurance participation rates, especially for the rural-urban migrants, to facilitate their social integration into cities for a more productive and stable labor force. For the migrants' smooth integration to achieve the high-quality urbanization, we also propose to deliver more affordable medical services through the competition by more private sector healthcare providers. Then a mandatory health insurance policy for all migrant employees, compensated substantially by employers, should be implemented to expand the coverage. Finally, a cross-region transfer of health insurance is also suggested to maintain the improving participation, especially for the low-income migrants.