As an important means of human survival and development, work has a non-negligible impact on residents' happiness. Based on the data of China Family Panel Studies of 2020, this paper examines the heterogeneous impact of job satisfaction on residents' happiness and its influencing mechanism. The results show that job satisfaction has a significant happiness enhancement effect. Heterogeneity test finds that job satisfaction has different happiness promoting effects on groups with different individual characteristics (gender, exercise frequency, family contact), different work experience (working hours, whether to distinguish working days, work flexibility), and different work experience (sleep time on working days, whether to be provided with year-end bonus as well as insurance). The mechanism test shows that job satisfaction affects residents' happiness through income increase effect, social reinforcement effect, confidence enhancement effect and expectation improvement effect.