The experiment chooses three kinds of perennial grasses, Elymus nutans, Festuca sinensis and Festuca ovina ,which distributed widely in the east of Qing-Hai Tibet alpine meadows and used a field replacement series to study the inter-specific competition. The experiment was of four total densities and two interference factors, fertilization and clipping. The competition ability of Elymus nutans was the strongest, then Festuca sinensis, followed Festuca ovina based on Relative Yield Total (RYT) and Competition Ratio (CR) which were calculated from harvested shoot dry weights.Fertilization and clipping had no obvious influence on the competition pattern. F. sinensis/E.nutans mixture sutilized the same resource and showed competitive trend when mixed at various seeding densities.In the F.ovina/E.nutans mixtures, they shared the same resource and showed the commensal relationship when density was lower. When density increased they utilized the same resource and showed competitive relationship. F. sinensis/F.ovina mixtures shared the same resource and facilitated each other. They showed the commensal relationship and it was density-independent.