Based on the Vegetation Map of China, the vegetation of southwest areas in China (including Yunnan, Guizhou, Sichuan Province, and Chongqing City) was classified into different plant functional types (PFTs), with the effective environmental factors of each PFTs determined. Combined with simulated future climate data (in 2050), the potential vegetation distribution of southwest areas in China was forecasted by Maximum Entropy Model. The results showed that:(1) According to the plant's canopy characteristics (coniferous/broad-leaved, evergreen/deciduous), the demand for water and temperature, and the actual vegetation data, the vegetation of studied areas was classified into fifteen PFTs, including six types of trees, six types of shrubs and three types of herbal. (2) The dominant factors affecting the distribution of tropical trees in southwest China were the lowest temperature of the coldest month and the annual average precipitation (with a total contribution rate of 90.3%). The distribution of subtropical PFTs were mainly affected by changes in temperature (with a contribution rate of 41.7%). The distribution of temperate PFTs was mainly affected by precipitation (with a contribution rate of 40.1%). Alpine meadow grasses and Alpine evergreen broad-leaved shrubs were mainly affected by temperature and altitude, while the cold deciduous broad-leaved shrubs were mainly influenced by precipitation. (3) With an increase in CO₂ emissions, the distribution of PFTs in southwest China would change as following in the future. First, the suitable area of tropical evergreen broad-leaved trees would gradually expand. Second, areas of high suitability (RCP8.5) for the subtropical deciduous woody plants would increase to 10.3% in 2050, which tend to move eastward. Third, the subtropical evergreen woody and herbaceous plants would occupy a wide range of functionally suitable areas (i.e., 86.5% of the total study area) and display irregular fluctuations under the scenario of future climate. The suitable areas for the temperate plants (except the temperate shrubs) would decrease to 13.6% in 2050 (RCP8.5), while that for the temperate evergreen coniferous shrubs would increase. The highly suitable area would move to the west and the area would increase to 8.25 times of the present area in 2050 (RCP2.6). The suitable area of the alpine plants would decrease with the highly suitable area moving eastward.