The study selected Ruoergai County in the northwest Sichuan Province as the study area,MOD17A3 was used to estimate the actual NPP. Based on Thornthwaite Memorial model to simulate potential NPP caused by climate change,using residual analysis to separate the influence of human activities exerted on NPP,and then utilizing the slope of one-variable linear regression equation to analyze the change tendency of each raster,a quantitative analysis was made for the impact of climate change and human activities in the study area from 2000 to 2010. The results indicated that at the regional scale,the grass of Ruoergai County in northwestern Sichuan showed a tendency of restoration as the rate of recovery area reached to 53.7% while the degradation area was within 46.3%. The degradation was mainly distributed in southeast and west of the study area. At the scale of 11 years,the contribution of human activities and climate change were respectively 76.22% and 23.78% ;the residual between potential NPP and actual NPP was 3 316.37 g C/(m~2·a),which showed the ecological protection and construction project had achieved significant results. At the time scale,there was a rising trend of humanactivity positive impact toward grass as human NPP regression slope is 37.30 from 2000 to 2010,indicating ecological project was a long-term design.