According to the principles of satellite remote sensing estimation, the relationships between vegetation index and biomass were analyzed to produce a method to assess biomass in Qinghai Province based on satellite data. These analyses were based on the normalized difference vegetation index (NDVI) monitored by the EOS/MODIS satellite, aboveground biomass measured on the ground, and meteorological monitoring data (temperature and precipitation), and revealed the factors affecting aboveground biomass in Qinghai Province. We detected a significant positive correlation (P<0.01) between forage yield (aboveground biomass) and NDVI at ground monitoring sites in different grassland types during the grassland growing season. The average aboveground biomass in Qinghai Province tended to slightly increase from 2003 to 2017. The minimum average biomass was 2622 kg·ha–1 in 2003, and the maximum average biomass was 3252 kg·ha–1 in 2010. The aboveground biomass decreased gradually from the southeast to northwest. The areas with the highest biomass were in the southeastern part of Guoluo Prefecture, Yushu Prefecture,Huangnan Prefecture, and Haibei Prefecture, and the area with the lowest biomass was in the northwest of the Qaidam Basin. The aboveground biomass in most areas of Qinghai Province tended to remain unchanged or increase from 2003 to 2017. The grassland biomass significantly decreased in Qumalai, Dulan, and Gande. Against a background of high temperature and sufficient heat conditions, grassland in Qinghai Province was favorably affected by greater water availability resulting from increased precipitation. Greater water availability played a role in promoting the growth and development of grassland vegetation in alpine regions, which eventually led to an increase in NDVI and biomass in those regions.