Abstract: Understanding the characteristics of urban expansion and corresponding spatial changes serves as a prerequisite for optimizing urban spatial structure and resisting disorderly urban land expansion. This study focuses on the Chengdu-Chongqing economic circle. Using multi-source data fusion, this study extracted information on urban built-up areas from 2000 to 2020. From the aspects of urban expansion characteristics, spatial changes, and intercity spatial interaction intensity, this study analyzed the spatiotemporal evolution during urban expansion at both the regional and county scales. The results indicate that incorporating impervious surface information into multi-source data fusion improved the information extraction accuracy of built-up areas, achieving an overall classification accuracy of 98% and an average Kappa coefficient of 0.75. Urban expansion from 2000 to 2020 transitioned from low to medium-high speed and then to low speed. The dominant expansion type was edge expansion, accompanied by decreased spatial compactness. Within the Chengdu-Chongqing economic circle, the strongest spatial interaction intensity occurred between Chengdu and Chongqing. The urban spatial pattern exhibited a “dual cores with two wings” pattern, highlighting the pivotal role of Chengdu and Chongqing in driving the development of surrounding cities. These findings reveal the urban development patterns and spatial change characteristics within the Chengdu-Chongqing economic circle. They will facilitate the rational optimization of land use and territorial spatial patterns, promoting coordinated urban-rural development.