Abstract: Based on the data from Rural-Urban Migration in China（Rumic）in 2007， 2008， 2016 and 2017， this paper return the equation of overwork selection and overwork hours of migrant workers， and decompose the change in time and intergenerational difference of migrant workes’ overwork based on the regression results to analyze the influence of individual characteristics， employment characteristics of migrant workers and the labor market environment on the change of migrant workers’overwork. The results show that the overall changes of individual characteristics and employment characteristics of migrant workers are conducive to the alleviation of their overwork. From the perspective of individual characteristics， improving the level of education is helpful to alleviate the overwork of migrant workers. From the perspective of the impact of employment characteristics， increasing the employment proportion of migrant workers in the state-owned sector， increasing the signing rate of migrant workers’labor contracts， and improving the enjoyment rate of basic social insurance will all help alleviate the overwork of migrant workers. The overall changes in the labor market environment increase the probability of migrant workers’ overwork， which is not conducive to the alleviation of their overwork. From the perspective of time change， the change of market environment increases the probability of migrant workers’overwork. From the perspective of intergenerational differences， the market environment makes the new generation of migrant workers more likely to overwork than the traditional generation. As the test results that the impact of the new labor contract law in 2008 on the overwork of migrant workers， it is shown that the measure of regulating the working hours and overtime pay is an effective way to alleviate the overwork of migrant workers. Therefore， the government department should pay attention to the improvement of the market regulation， limit the work behavior of enterprises by establishing more stringent overtime wage system， such as specify overtime pay and time limit， make wage rates increases with the extension of overwork hours， etc. These measures not only can reduce the probability of migrant workers’ overwork， also helps to reduce the extent of migrant workers’ overwork.

Keywords: Migrant Workers， Overwork， Working Hours， Market Environment