With the transition from a planned economy to a market economy, great changes have taken place in China’s labor market in the past 40 years. These are reflected in two main aspects: first, labor resources have changed from planned allocation to market allocation, and second, China’s long-standing urban–rural division and dual labor market are gradually changing into a national integrated labor market. The market is playing an increasingly important role in the allocation of labor resources. In the past 40 years, the most obvious phenomenon in China’s labor market has been the influx of hundreds of millions of rural laborers into cities. The reallocation of labor resources between urban and rural areas has met the needs of urban economic growth, produced a sustained increasing income effect, and helped achieve the miracle of China’s economic growth. This important economic phenomenon has aroused widespread concern in academic circles and produced a large number of discussions and academic research results. This chapter summarizes the basic situation of urban–rural labor migration in the past 40 years, summarizes the contribution of urban–rural labor migration to economic growth, analyzes the mechanism of its economic impact, and discusses a series of important social issues associated with urban–rural labor migration.