Climate change scenarios predict increases in temperature, changes in precipitation patterns and longer drought periods in most arid and semi-arid regions of the world. Land-use type changes are considered to be the dominant component of global change in terms of impacts on terrestrial ecosystems. Ecosystems in these regions are prone to land degradation, which may be aggravated by climate change. With a changing climate, the effect of different use types and the intensity of changes in the spatial patterns of precipitation will combine to determine ecosystem vegetation types, net primary productivity and C accumulation in the grassland ecosystems of Inner Mongolia, China. A field experiment with different land use types was conducted in two important grassland types in Inner Mongolia: desert steppe (a site in Sunite Banner) and typical steppe (a site in Baiyinxile Banner) to study the response of arid and semi-arid grasslands to different land-use types and precipitation. The change of above-ground net primary productivity (ANPP) and below-ground net primary productivity (BNPP) for each plant community was studied and C accumulation of the plant communities were also assessed for four different land use types 1) enclosure, 2) rotational grazing, 3) clipping and 4) grazing during two hydrologically contrasting growing seasons (a dry season and a wet season) both in a desert steppe and in a semiarid steppe. The results follow: 1) In the deficit precipitation year, compared with the enclosure, ANPP, BNPP and C accumulation decreased by 57.1%, 51.7% and 56.0% and by 18.4%, 25.1% and 17.9% under grazing in the desert steppe and the typical steppe, respectively; meanwhile, in the adequate precipitation year, compared with enclosure, ANPP, BNPP and C accumulation increased by 18.2%, 9.8% and 21.9% under rotational grazing in the desert steppe, respectively, whereas ANPP was still the highest in enclosure in the typical steppe; 2) Different grassland use types also have a significant effect on ANPP, BNPP and C accumulation. Compared with other use types, the grazing enclosure was a reasonable land use types both in desert and typical steppe to increase ANPP, BNPP and C accumulation; 3) The different grassland use types had different responses to the change of interannual precipitation. The effect of precipitation on grazing was higher than on other land use types in both the desert steppe and the typical steppe; 4) The ANPP in the wet year was twice that of the dry year in the desert steppe, but ANPP only increased by 79.0% in the wet year when compared with the dry year in the typical steppe. The impact of precipitation was larger on the desert steppe than on the semiarid steppe. ANPP, BNPP and C accumulation in arid and semiarid ecosystems are primarily limited by precipitation. A change of temporal and spatial patterns for precipitation plays an important role in determining ANPP, BNPP and C accumulation. Under future climate change scenarios, precipitation and grassland use types were the principal environmental factors affecting plant community net primary productivity and C accumulation in the arid and semi-arid steppe in northern China.