Abstract:In order to explore the spatiotemporal evolution of the central cities in the Chengdu-Chongqing Urban Agglomeration (CCUA), reveal the driving mechanisms, and simulate the future direction of urban spatial expansion based on the construction background of Chengdu-Chongqing Economic Circle (CCEC), an in-depth analysis is conducted by using methods such as urban spatial characteristics measurement, geographical detectors, and the FLUS model. The results are as follows: 1) From 1980 to 2020, the central cities in the CCUA experienced rapid spatial expansion, with a significant increase in urban scale and a rising trend in expansion intensity. The compactness index of central cities showed a downward trend, while the fractal dimension showed a trend of first increasing and then decreasing, with obvious irregularization and discretization of urban spatial forms. The urban spatial expansion of Chengdu formed a “concentric circle layer expansion” mode, mainly “circle layer and radiated”; while the urban spatial expansion of Chongqing formed a “multi-center, multi-group” mode. 2) GDP, population, transportation, and development zones are the main driving factors for the spatial expansion of central cities in the CCUA. The rapid economic development attracts a large population to gather, becoming the fundamental driving force for urban spatial expansion, promoting the rapid expansion of urban space. The continuously forming highway network pattern within and outside the city and the planned and newly built development zones have a significant traction effect on the direction of urban spatial expansion, and are the most direct driving factors in the process of urban spatial expansion. 3) The simulation results show that the central cities of the CCUA will continue to expand outward based on the original urban space in the future, while the traction effect of policy planning elements on urban spatial expansion will become more prominent. The urban space will break through terrain constraints in reverse and expand towards each other, forming a new urban spatial pattern. The above research results suggest that there are differences in the spatial expansion process of central cities in the CCUA, with the main driving factors shifting from natural factors to economic and social factors, and the interaction of attraction among central cities gradually becoming prominent. It is recommended that the strategic kinetic energy of the CCEC should be fully utilized in the future, the urban spatial structure should be optimized, the development of small and medium-sized cities in the central part of the Chengdu-Chongqing region should be promoted, and the urban system of the region should be optimized and improved.