Health insurance, as a key social security measure, impacts residents' well-being. This paper uses data from the China Health and Retirement Longitudinal Study (CHARLS) from 2015 to 2020 and employs the Difference-in-Differences (DID) method to empirically analyze the potential impact of the integration of basic medical insurance for urban and rural residents on the happiness of middle-aged and elderly people. It is found that the integration of basic medical insurance for urban and rural residents can significantly increase the life satisfaction of middle-aged and elderly people. The study passes the robustness test. Further heterogeneity analysis shows that, in terms of health status, the policy had a significant happiness-enhancing effect on middle-aged and elderly people with poor self-assessed health status in 2018, but by 2020, this enhancing effect was mainly reflected in the group with better health status. In terms of income level, the happiness enhancement of both low-income and high-income groups was more significant in 2018, while by 2020, the low-income group's well-being enhancement effect was more prominent. This study provides a theoretical basis for the policy design of 'targeted health insurance..