[Objective] The dynamic changes of NDVI under the influence of human and natural factors in Southwest China were studied in order to provide a basis for the scientific implementation of natural forest protection policies in this region.[Methods] Based on MODIS NDVI, land use data and climate data from 2001 to 2018, combined with Theil-Sen median trend analysis and Mann-Kendall trend test, the dynamic changes of vegetation under human and natural factors in the Southwest China were investigated.[Results] ① NDVI of all types of vegetation increased year by year, with the fastest growth in agricultural land and savanna. The east of Minjiang and Wumeng Mountains was the region with high NDVI value and significant improvement trend; Combined with the southern margin of the Yunnan-Guizhou Plateau, the trend area of significant improvement accounted for 67.09% of the total area. ② One of the reasons for the increase of NDVI in Southwest China was that the natural forest protection and the forestry policy of returning farmland to forest/grassland promoted the transformation of low NDVI vegetation to high NDVI vegetation. The largest contribution was the conversion of woody savanna and savanna to forests. From 2001 to 2018, the conversion area reached 73 693 km², and the net conversion rate increased year by year, mainly distributed in the east part of the boundary of Minjiang River and Wumeng Mountain. ③ The positive correlation between temperature and NDVI was greater than that of annual precipitation. In the east of Minjiang River and Wumeng Mountains, the positive correlation between NDVI and meteorological elements was high. Under the condition of warming and getting wetter, 41.8% of NDVI growth was related to temperature and precipitation, and their contribution rates were 32.35% and 14.54% respectively.[Conclusion] With the implementation of natural forest protection policy and the warming and humidifying regional climate change in the last 20 years, the NDVI in the Southwest China continued to increase from 2001 to 2018. Based on the boundary of the Minjiang River and Wumeng Mountains, such increasing characteristics showed differences in the east and west parts, and the increasing forests area and the NDVI improvement trend on the east side was generally higher than that of on the west side.