Objective: Taking the integration of urban and rural residents' medical insurance as an opportunity, the paper analyzes the impact of urban and rural medical insurance integration on catastrophic medical expenses of rural residents, and evaluates the effects of urban and rural medical insurance integration policy. Methods: This article uses China Family Panel Survey (CFPS) data from 2016, 2018, and 2020, and adopts a multi-period DID model to empirically evaluate the impact of urban and rural resident medical insurance integration on catastrophic medical expenditures of rural residents. Results: The integration of medical insurance for urban and rural residents reduced the incidence of catastrophic medical expenses for rural residents by 9%. Based on age groups, the integration of medical insurance for urban and rural residents reduced the incidence of catastrophic medical expenses by 0.16% in the groups aged 18~34, but increased the incidence of catastrophic medical expenses by 3% in the elderly population aged 55 and above, with no significant impact on the middle-aged population aged 35~54. Based on income groups, the integration of medical insurance for urban and rural residents reduced the incidence of catastrophic medical expenses for low and middle-income families by 7.4%, but the impact on high-income families was not significant. Conclusion: The integration of medical insurance for urban and rural residents has reduced the incidence of catastrophic medical expenses for rural residents, promoted the narrowing of the gap in healthcare security levels between urban and rural residents, and achieved the expected effect for low and middle-income groups. However, further attention should be paid to the risk of medical expenses for the elderly, and compensation policies should be implemented for the elderly in the future.