Net primary productivity (NPP) and its responses to global change is one of the focuses of global change research. Based on MODIS NDVI data, land use classification data and meteorological data, spatio-temporal changes of the NPP of Inner Mongolia vegetation during 2001-2010 were simulated using improved light use efficiency model (CASA model). The relationships between NPP and climate factors were analyzed based on partial correlation coefficients of the two-group elements. The results showed that average annual NPP from 2001 to 2010 was 340.0 gCm^-2a^-1 in the study area, exhibiting obvious increase trend from southwest to northeast with a mean change rate of 200.5 gCm^-2a^-1/10°. The mean NPP of forest, grassland, cropland and desert were 521.9、270.3、405.7 and 85.3 gCm^-2a^-1, respectively, which showed significant differences. During 2001-2010, the average annual total NPP of Inner Mongolia vegetation was 322.7 TgCa^-1, ranging from 276.8 to 354.4 TgCa^-1. Over the 10 years period, extremely significant increase of vegetation NPP occurred in Alxa desert, the western margin of Mu Us sandy land, north of Hetao plain, the eastern and western margin of Hunshandak sandy land and northwest of Hulun Buir league, while extremely significant decrease of vegetation NPP mainly occurred in the grassland in the central of Inner Mongolia. Climate factors exerted various influences on different vegetation types. Temperature was the dominant driving force of NPP of forest, while precipitation influenced the NPP of grassland, cropland and desert vegetation more seriously.