Grassland is the main ecosystem type in the eastern Inner Mongolia, which belongs to the fragile ecosystem and is sensitive to climate and human activities. Based on land cover data and the improved CACS model, the grassland NPP(net primary productivity) was estimated, and the spati-temporal dynamics of grassland and NPP in the eastern Inner Mongolia from 2000 to 2015 were analyzed. Furthermore, the relative degradation index (RDI) was defined to determine the contribution rate of human activities in the process of grassland productivity change, and the spatial pattern and interannual dynamics of RDI in the eastern Inner Mongolia from 2000 to 2015 were analyzed. At the same time, the correlation between NPP and climatic factors during the past 16 years was inverstigated. Results showed that: 1) during 2000-2015, the loss and increase of grassland area was 4743.80 km² and 2705.57 km², respectively. 2) From 2000 to 2015, the average NPP of grassland in the eastern Inner Mongolia ranged from 166.56 to 248.14 gC m^-2 a^-1. NPP showed an obvious upward trend in fluctuation (3.65 gC m^-2 a^-1/a, R²=0.47). 3) From 2000 to 2015, RDI fluctuated between 16.64% and 30.54%, and the RDI value showed a slow downward trend, indicating that the influence of human activities on grassland-NPP was decreasing. 4) The main reason of NPP change is the decrease of grassland productivity. Overall, the grassland protection work had made phased progress, and grassland habitat quality and ecological environment had been effectively improved.