This study, based on a questionnaire survey of production line workers of 12 coal mines across four provinces, and by using correlation and multiple regression analysis, explores the key influence factors of production line workers' overwork in coal mines in China across the four aspects of the individuals, their families, enterprises and their work. The results of the study indicate that the following factors of their economic interests, self-development, family responsibilities, inharmonious family relations, assessment standards, salary systems, corporate cultures, workloads, work requirements, and working environments have a significant positive impact on the overwork of production line workers in coal mines, whereas their family support has a significant negative impact on the overwork of those in coal mines. Furthermore, significant differences also exist in the degree of overwork among workers of different ages, working years, and incomes. The older the workers, the longer their working years, and the higher their income, the higher their degree of overwork is. Overall, the production line workers' overwork in coal mines is common and serious.