Abstract: The effect of species diversity on ecosystem function is one of the core issues in ecology. Our objective was to explore the relationship between species diversity, productivity, climatic factors, and soil nutrients in the desert steppe, to enhance understanding of the diversity-productivity relationship. Species richness and Shannon-Wiener index were used to measure species diversity. Climatic, vegetation and soil data were collected for 80 sampling sites across the desert steppe of Inner Mongolia. Regression analysis and stepwise regression analysis were used for determining the relationship between environmental factors and species diversity and productivity. The effects of environmental factors on species diversity and productivity were evaluated, based on the coefficient of determination from regression analysis. It was found that species diversity and biomass were both positively and linearly correlated with mean annual precipitation and aridity index. However, Shannon-Wiener index and biomass were both negatively and linearly correlated with mean annual temperature. Species richness was negatively and linearly correlated with soil total phosphorus content (R²=0.072, P<0.05), but positively and linearly correlated with soil available nitrogen content (R²=0.183, P<0.01); Shannon-Wiener index was also positively and linearly correlated with soil available nitrogen content (R²=0.061, P<0.05), and biomass was positively and linearly correlated with total nitrogen, soil available nitrogen, and soil organic carbon content. The coefficients of determination were 0.150, 0.177, 0.089 (P<0.01), respectively. Biomass increased significantly with the increase of species richness and Shannon-Wiener index. These results indicate that aridity index is the most influential factor affecting species diversity and biomass of desert steppe.