Based on the data of China Family Panel Studies in 2012 and 2014, and by establishing the overwork selection equation, the labor time regression equation, and the overwork persistence equations of migrant works, this paper analyzes the impact factors of migrant workers’ overwork. The results indicate that the low wage level is a key cause of excessive overwork for migrant workers. The paper suggests higher levels of education may contribute to reducing the probability of migrant workers’ overwork and continuous overwork; and signing of labor contracts may assist to reduce the probability, the degree, and persistence of migrant workers’ overwork. Moreover, the study also shows that there is also a significant difference in migrant workers’ degree of overwork in different occupations, and their overwork becomes more common in overcrowded occupations. As a result, as long as the basic income of migrant workers is guaranteed, governmental institutions should help to improve their educational level and technical skills, increase their employment stability, and eliminate occupational segregation. Only in this way can migrant workers’ overwork be alleviated