As a fundamental constituent of global terrestrial biomes, vegetation serves as a critical mechanism for atmospheric carbon sequestration through photosynthetic assimilation while concurrently maintaining ecological equilibrium via biodiversity conservation. Based on the Normalized Difference Vegetation Index (NDVI), land use, and climate datasets, this study analyzed the changing trend of vegetation growth and clarified the impact of climate change and urban expansion on vegetation variation in southwest China by the ensemble empirical mode decomposition, partial correlation analysis, and segmented linear regression. The results showed that vegetation NDVI in southwest China increased, indicating an obvious vegetation greening trend; spatially, high NDVI values were found in the southeastern part, and the regions with low NDVI were concentrated in the northwestern part. Compared to solar radiation and precipitation, the driving scale and degree of temperature on regional vegetation growth were relatively large, accounting for approximately 64.6% of the study area, mainly distributed in the central and western parts of the study area. Land urbanization, economic urbanization, and population urbanization increased over time, and the spatial distribution of these three urbanizations was relatively consistent. At the county scale, the correlation between economic urbanization, population urbanization, and vegetation growth increased first and then decreased, showing a nonlinear characteristic; a negative correlation was revealed between land urbanization and vegetation growth. At the grid scale, the relationship between these three urbanization and vegetation growth remained unchanged; but there were significant differences in the thresholds of nonlinear relationships. This study can provide a scientific reference for implementing more precise ecological management measures and achieving sustainable socio-economic development in this region.