Soil carbon pools could become a CO_2 source or sink, depending on the directions of land use/cover changes. A slight change of soil carbon will inevitably affect the atmospheric CO_2 concentration and consequently the climate. Based on the data from 127 soil sample sites, 48 vegetation survey plots, and Landsat TM images, we analyzed the land use/cover changes, estimated soil organic carbon(SOC) storage and vegetation carbon storage of grassland, and discussed the impact of grassland changes on carbon storage during 2000 to 2013 in the Ili River Valley of Northwest China. The results indicate that the areal extents of forestland, shrubland, moderate-coverage grassland(MCG), and the waterbody(including glaciers) decreased while the areal extents of high-coverage grassland(HCG),low-coverage grassland(LCG), residential and industrial land, and cultivated land increased. The grassland SOC density in 0–100 cm depth varied with the coverage in a descending order of HCG>MCG>LCG.The regional grassland SOC storage in the depth of 0–100 cm in 2013 increased by 0.25×1011 kg compared with that in 2000. The regional vegetation carbon storage(S_(rvc)) of grassland was 5.27×10~9 kg in2013 and decreased by 15.7% compared to that in 2000. The vegetation carbon reserves of the under-ground parts of vegetation(S_(ruvb)) in 2013 was 0.68×10~9 kg and increased by approximately 19.01%compared to that in 2000. This research can improve our understanding about the impact of land use/cover changes on the carbon storage in arid areas of Northwest China. Soil carbon pools could become a CO 2 source or sink, depending on the directions of land use / cover changes. A slight change of soil carbon will inevitably affect the atmospheric CO 2 concentration and therefore the climate. Based on the data from 127 soil sample sites, We estimated the land use / cover changes, estimated soil organic carbon (SOC) storage and vegetation carbon storage of grassland, and discussed the impact of grassland changes on carbon storage during 2000 to 2013 in the Ili River Valley of Northwest China. The results indicate that the are extents of forestland, shrubland, moderate-coverage grassland (MCG), and the waterbody (including glaciers) decreased while the are extents of high-coverage grassland (HCG), low- coverage grassland (LCG), residential and industrial land, and cultivated land increased. The grassland SOC density in 0-100 cm depth varied with the coverage in a descending order of HCG> MCG> LCG. l grassland SOC storage in the depth of 0-100 cm in 2013 increased by 0.25 × 1011 kg compared with that in 2000. The regional vegetation carbon storage (S_ (rvc)) of grassland was 5.27 × 10 ~ 9 kg in2013 and decreased by 15.7% compared to that in 2000. The vegetation carbon reserves of the under-ground parts of vegetation (S_ (ruvb)) in 2013 was 0.68 × 10 ~ 9 kg and increased by 19.01% compared to that in 2000. This research can improve our understanding about the impact of land use / cover changes on the carbon storage in arid areas of Northwest China.