Based on the panel data of Beijing metropolitan area from 2000 to 2017, this paper uses dynamic GMM estimation method to analyze the agglomeration effect of Beijing metropolitan area and its inner layers. The results show that: (1) on the whole, the population aggregation and economic growth in Beijing metropolitan area show an inverted U-shaped relationship of first rising and falling,and the population size of Beijing metropolitan area has exceeded the optimization point; (2) from the perspective of each circle, the continuous growth of population scale in the core circle and close circle of Beijing metropolitan area is more manifested as crowding effect, that is, it has a negative impact on economic growth, while in the opportunity circle, it is more manifested as clustering effect And significantly promote output growth. In the future, the population relief from the core circle and close circle to the opportunity circle of Beijing metropolitan area will help to improve the overall development balance of Beijing metropolitan area.