Working hour system is the result of comprehensive effect of many factors such as labor efficiency, workers* health level, and socioeconomic development level. Based on the perspective of ''moderateness", this study conducted a literature review of working hours and found that the game between labor and management runs through the long process of evolution of the working-hour system, and the "over** and "low" of working time both have a negative impact on labor and socio-economic development. Hence, appropriately shortening working hours is beneficial to the physical and mental health of workers and labor productivity increase. Other different factors such as gender, occupational differences, working environment, and increase or decrease in social welfare, will also affect the determination of appropriate working hours. Further in-depth research is required on issues of overwork, degree of shortened working hours, and use of flexible working hour systems.