Flexible employment is becoming an increasingly important component of China’s labor market. At the same time，mental health challenges faced by this group are also aggravating. Based on the China Family Panel Studies（CFPS）data from 2016 to 2020，this study employs the multi -period Difference -in -Differences （DID）model，Propensity Score Matching（PSM），heterogeneity analysis，and mediation effect test to study the impact of the integration of urban and rural resident medical insurance policies on the mental health of flexible employees. The results revealed that the insurance integration policy significantly improved the mental health status of flexible employees，particularly among the young，rural household registrants and those in western regions. Health expenditure pressure played a mediating role in the impact of the policy. The findings of the study hold practical significance for deepening the reform process of integrating urban and rural resident medical insurance，continuously expanding the coverage of medical insurance to flexible employees，and raising the awareness of the variation in mental health among flexible employees with different characteristics.