Soil water-stable aggregates are the base of soil fertility. The content of water-stable aggregates was measured under controlled conditions to determine how short-term grazing influences soil aggregate stability and biomass in an alpine meadow on the northeastern edge of the Qinghai-Tibetan Plateau. Results showed that the content of water-stable macro-aggregates increased under moderate grazing. Organic carbon in water-stable aggregates was reduced with increasing soil depth. Compared with the control, organic carbon in > 1 mm water-stable aggregates within 10 cm of soil surface was significantly reduced under moderate grazing, but < 1 mm water-stable aggregates in the 10-20 cm soil layer increased. The biomass was significantly increased within 10 cm of soil surface with the increasing grazing intensity. Rhizosphere soil under moderate grazing had the largest amount of fungi and the number of actinomycetes increased with the increasing grazing intensity.