Community biomass and species diversity are important indicators to characterize the quantitative characteristics of grassland ecosystems. This study conducted in the grasslands of the Tworiver Source grazing areas in the southern Altai Mountains of Xinjiang and a survey of grassland vegetation in different grazing areas of the Tworiver Source using the sample method, analyzed the changes in biomass and species diversity in the study area, and explored the correlation between the two and environmental factors, in order to provide a theoretical basis for the conservation of grassland community species and sustainable use of grassland. The results showed that: (1) there were differences in community cover, height, plant density, aboveground biomass and biomass per unit of cover among different grazing areas in the Tworiver Source. (2) The aboveground biomass of grassland communities in the Tworiver Source rangelands was significantly and positively correlated with community cover and plant density (P<0.05), and aboveground biomass was mainly influenced by the cover of grassland communities. The species diversity index varied somewhat among the different grazing areas, but the species distribution was relatively uniform. (3) Grassland community biomass and species diversity in the Tworiver Source rangelands are mainly influenced by temperature and precipitation.