Abstract: Nostoc commune belongs to Nitrogenfixing blue algae, and the characteristic of its nitrogenfixing is reversible. It plays an important role in the nitrogen cycle of natural grassland. In order to provide an information on grassland utilization and management, the effects of grazing, cutting, firing and fencing on the biomass dynamics of N.commune in Bashang grassland were investigated in this study. The results indicated that fencing promoted the growth of N.commune, and the highest total biomass occurred in fencing treatment, followed by moderate grazing and cutting, the lowest biomass occurred in heavygrazing treatment and it only accounted for 11.2%-35.1% of those in fencing treatment. Firing showed significant negative effects on the growth of N.commune, there was no N.commune in year one after firing, but with the standing dead litter and litter increasing in year two after firing, N.commune began to grow and increased. Biomass of N.commune showed positive correlationship with standing dead litter and litter. Biomass of standing dead litter and litter were the main determinated factors on biomass of N.commune in Bashang natural grassland. In conclusion, fencing and moderate grazing promoted growth of N.commune and increased nitrogenfixing in grassland.