Research on the Impact of Polycentric City Network on Economic Growth in the Yangtze River Delta Urban Agglomeration

The Yangtze River Delta region is facing the demand for high-quality economic development, and the study of urban network as a manifestation of the interaction between cities is becoming increasingly important. This study focused on the node structure of the urban network in the Yangtze River Delta urban agglomeration from 2010 to 2021, used the modified gravity model to construct a polycentric city network from the perspective of economic flow, used the spatial Durbin model for spatial econometric analysis, and identified the conduction path through the two-step method of causal stepwise regression mediating effect test. The results show that Shanghai, as the core node city, has significantly promoted the economic development of Hangzhou, Nanjing, Hefei, and other cities and formed a metropolitan network structure characterized by “one core and five circles”. Under different spatial weight matrices, the polycentric city network has a significant positive impact on economic growth, and its impact is not only related to the economic level of the city itself but also closely related to the economic status of its neighboring cities. The polycentric city network significantly enhances economic growth by accelerating the flow of regional factors, promoting regional industrial division of labor and cooperation, and enhancing regional innovation capabilities.