Vegetation growth, through photosynthesis, takes up carbon dioxide from the atmosphere and converts to organic carbon into biomass thereby forms a carbon sink. Research on carbon sequestration potential of forests has become a key content to slow down global warming by forestry. To assess carbon sequestration potential in stands under the Grain for Green Program (GGP) in Southwest China, the carbon storages and their annual changes in the GGP-stands in the region were estimated based on: (1) collected data on annual planted area of each tree species under the GGP in Southwest China from 1999 to 2010; (2) empirical growth curves developed for each species of the GGP-stands using growth data about plantation from the National Forest Inventory; (3) parameters associated with stand such as wood density, biomass expansion factor, carbon fraction, the change rate in soil organic carbon content. Two scenarios for forest management option were schemed: scenario A for no harvesting and scenario B for logging at the time of maturity followed by replanting. The results showed that there are seven tree species with over 100,000 hm² of planted area in Southwest- China throughout the recent goal period of strategic planning for the GGP, and their total acreage account for 40.7% of that of all species of the GGP-stands. The expected carbon stocks in these major stands under the Grain for Green Project in Southwest China are52.98TgC, 73.88-80.57TgC, 73.63-102.16TgC, 88.41-115.17TgC and 77.15-123.36TgC(T=10¹²) by the year of 2020, 2030, 2040, 2050 and 2060, and the estimated relevant annual carbon stock changes are 3.15TgC, -1.11-2.45TgC, -3.92-1.95TgC, 2.08-0.96TgC and 0.25-0.73TgC, respectively. In 2060, the carbon stocks in forests of Pinus armandii, Pinus massoniara, Cryptomeria fortunei, Cunninghamia laceolata, Cupressus spp., Populus deltoides and Eucalyptus spp.under the Grain for Green Project in Southwest China will be 13.01TgC, 15.01TgC, 13.44TgC, 24.13TgC, 28.05TgC, 15.63TgC和14.09TgC, respectively, indicating a significant contribute to forest carbon sinks in this region. The Cupressus spp. species play a leading role in carbon sequestration potential in stands under the Grain for Green Project due to highest area proportion in Sichuan province, Chongqing municipality and even Southwest China. The Cryptomeria fortune and Cunninghamia laceolata species play a leading role in Guizhou province; the Eucalyptus spp. and Pinus armandii species in Yunnan province; the Populus deltoides species in Tibet autonomous region.