Using data at micro and city levels, the present paper explores the policy evolution of the minimum wage system in China, and examines its coverage for migrant workers. The analysis indicates that minimum wage policy has been substantially improved in terms of both coverage and the level of the minimum wage standard, but that the current policy tool that relies on the monthly wage rate is not effective. Because migrant workers tend to work more hours, use of an hourly wage rate is more appropriate than a monthly wage rate.