Working hours have a signifi cant impact on the health of employees. This study, based on data from the China Family Panel Studies in 2018, employs regression analysis and Utest test methods to verify the relationship between working hours and a variety of health indicators of employees and computes the critical value of working hours. The study claims that working hours has an inverted U-shaped relationship with selfrated health, mental health, and chronic disease indicators, with critical values of 45.075 hours/week, 35.550 hours/week, and 53.100 hours/week respectively with heterogeneities between urban and rural areas. Working hours have an inverted U-shaped relationship with the self-rated health and mental health of urban employees. Also, there is an inverted U-shaped relationship between working hours and self-rated health of rural employees. Moreover, there is a linear relationship between working hours and the mental health of rural employees. The critical value of self-rated health for urban employees is greater than that for rural employees. The study suggests that limited overtime should be advocated and overtime compensation should also be made. In addition, the government should vigorously promote employment, in particular, improving the quality of employment for rural employees.