Abstract:Urban development in the southwest of China started late and at a low level, the study on the spatial and temporal changes of urban expansion in Southwest China and quantitative driven analysis can provide a reference for the future development of mountainous cities. The study is based on the capital cities of Yunnan, Guizhou, and Sichuan provinces. The built-up areas of Kunming, Guiyang, and Chengdu were extracted using Landsat images from 1990 to 2020 and combined with the urban plan. Various spatial-analysis measures were used to analyze the spatial and temporal characteristics of the built-up areas among these cities. Based on the structural equation model, using a number of socio-economic data to examine the drivers of urban development. The results show that: (1) During 1990-2020, the expansion rate of the three cities continued to increase, the intensity of expansion first increased and then decreased, the city boundaries continued to lengthen, the compactness continued to decrease, the distance between the spatial center of the city continued to increase. The process of urban spatial expansion was relatively rough. (2) During 1990-2020, the expansion pattern is mainly "strip-like" and "star-shaped filling", and the direction of urban expansion is mainly forced by the mountain range. The mountainous relief affects the urban construction process (3) The total effect of social factors driving urban spatial expansion is the largest, followed by demographic and economic factors, and the total effect of each factor driving urban expansion can be ranked as follows: social factors (1.294) > demographic factors (0.863) > economic factors (0.742). The results of the study can provide scientific advice for urban development planning in mountainous areas.