Abstract: Background Southwest China (Yunnan, Guizhou, Sichuan, and Chongqing), highly prone to erosion, faces significant ecological and soil-water conservation challenges due to rapid socioeconomic development and land use change. However, research on future land use changes under diverse socioeconomic scenarios in this critical region remains limited. This study simulated future land use changes to inform land resource management and ecosystem protection strategies, particularly for soil and water loss prevention. Methods Based on MCD12Q1 historical land use data (2001-2020) and LUH2 future data, the Patch-generating Land Use Simulation (PLUS) model was used to simulate land use distribution from 2020 to 2100 under three Shared Socioeconomic Pathway-Representative Concentration Pathway (SSP-RCP) scenarios: SSP1-RCP1.9 (Sustainable Development), SSP2-RCP4.5 (Medium Development), and SSP5-RCP8.5 (High-speed Development). Spatiotemporal characteristics of change were analyzed using land use dynamics, transition matrices, and spatial expansion analysis. Results 1) Historically (2001–2020), forest area increased significantly by 42,191 km² (reaching 47.73% coverage), primarily converted from grassland (-52,614 km²). Urban expanded by 42.35%, concentrated in agglomerations like the Chengdu-Chongqing. 2) The PLUS model demonstrated high accuracy (Kappa = 0.85, OA = 0.91, FoM = 0.18). Future simulations (2020-2100) revealed strong scenario dependence: SSP119 exhibited peak land use intensit (comprehensive dynamic degree: 1.71%), with dramatic forest (+57.33%) and cropland (+66.96%) increases but severe grassland decline (-96.23%). Forest covered most regions except the Sichuan Basin, and cropland expanded in northwestern/eastern Sichuan, eastern Yunnan, and central/western Guizhou. SSP245 showed moderate changes (forest: +10.18%, cropland: +18.40%, grassland: −19.21%). SSP585 exhibited high early-period intensity (pre-2040), featuring concentric urban expansion within clusters, converging towards SSP245 patterns by 2100. Grassland consistently remained the primary conversion source across all scenarios. Built-up land followed an inverted U-shaped trajectory, peaking in the 2050s. Conclusion The PLUS model reliably simulates long-term land use changes in Southwest China’s complex terrain. Multi-scenario outcomes reveal divergent policy-relevant pathways: SSP119 drives extensive ecological conversion (forest/cropland increase, grassland loss), while SSP245/SSP585 show moderated changes with mid-century urban peaks. These projections provide a robust scientific basis for optimizing territorial spatial planning and sustainable land management to support soil and water loss prevention and broader ecological protection goals.