Abstract: The lower Jinsha River region holds significant ecological importance and is home to the world’s largest hydropower base. Understanding the spatiotemporal dynamics of vegetation coverage in this area can provide valuable insights for ecological conservation and sustainable development in the basin. This study analyzed vegetation coverage changes and associated influencing factors across different stages of hydropower development (2000–2022), using MODIS NDVI (Normalized Difference Vegetation Index) data. We employed methods of Theil-Sen Median trend analysis, BEAST (Bayesian Estimator of Abrupt change, Seasonality, and Trend), and the Geographical Detector model. The results revealed that: (i) Over the past 23 years, vegetation NDVI around the lower Jinsha River region exhibited a fluctuating increase. NDVI increased from 0.460 to 0.515 in the Xiluodu-Xiangjiaba segment (Xi-Xiang section) and from 0.432 to 0.476 in the Wudongde-Baihetan segment (Wu-Bai section). Following the completion of the hydropower station, vegetation improvement predominated, with the areas of significant and slight improvement accounting for 85.25% and 66.93% of the study region, respectively. (ii) Trend components of NDVI in the Xi-Xiang and Wu-Bai sections experienced five abrupt changes, and the decline consistently coincided with reservoir impoundment periods. Nonlinear NDVI change pattern, such as monotonic increases, interrupted increases, and shifts from decline to increase, were observed. (iii) Elevation, temperature, slope, and precipitation were the key drivers of NDVI changes in the Xi-Xiang section, while elevation, evapotranspiration, temperature, and precipitation significantly influenced the Wu-Bai section. Socioeconomic factors, including land use, night-time light, and population, showed an increased influence after reservoir construction. Significant interactions between elevation, climatic, and socioeconomic factors were observed, which exhibited dual-factor enhancement and nonlinear effects.