Comparative survey of biomass of grass aboveground and underground was carried out in slightly degraded grassland ,medium degraded grassland and severely degraded grassland before forbidden grazing and after forbidden grazing in alpine meadow grassland in Qinghai .The results showed that aboveground biomass of and grasses each increased 3.15and 4.59 percent point and underground biomass of and grasses each increased 2.87and 4.30 percent point, aboveground biomass of weeds decreased 8.10 percent point and underground biomass of weeds decreased 7.17 percent point.