Ganzi prefecture is one of the important pasture,local ecological environment and economic development were affected by it's grassland changes.This paper evaluates the grassland growth in Ganzi prefecture in the 2005-2015with the net primary productivity(net primary productivity,NPP)of vegetation,the relative contribution of climate and human activities to grassland change was quantitatively assessed by using the net primary productivity model of integrated natural vegetation and residual analysis method,and on the basis of it,the correlation between climatic factors and elevation and annual variation and spatial distribution of NPP were analyzed.The results showed that:(1)The average NPP of the study area from 2005to 2015 was 286.6gC/m~2,the NPP was fluctuating,and the grassland generally presents a tendency of slow degeneration.(2)The relative contribution rates of climate,human activity and the combination of the two to grassland change were 26.5%,61.1%and 12.4%respectively,human activity was the main driving force of grassland degradation,and climate and human activity were the leading factor in the grassland restoration.(3)NPP changes were positively related to the annual average temperature and sunshine duration,and were negatively related to elevation and rainfall,the annual precipitation of the NPP was the most significant.