Abstract: Tibetan Plateau is one of the regions that are most sensitive to global change. In the past decades, Northern Tibet experienced significant warming. In this study, opentop chambers (OTCs) were used to simulate warming in alpine meadow in Northern Tibet. A warming gradient was generated by using different heights of OTCs (40, 60, 80 and 100 cm). The responses of plant growth, community composition and structure, and aboveground biomass to warming treatments were investigated. Under the series of treatment, air temperature increment ranged from 1.13 to 2.72 ℃. The temperatures in upper layer soil were also increased, accompanied by the decreased air and soil humidity. Kobresia pygmaea is the primary dominant species in the targeted communities. With increasing temperature, the importance value of K. pygmaea and the cover of sedges decreased. The warming effect on community growth and aboveground biomass accumulation varied with the warming magnitude. Warming promoted plant growth when it was lower than 2.1 ℃. When the warming magnitude was greater than 2.1 ℃, its stimulation effect was weakened, even prohibited plant growth. This study illustrated that the alpine meadow in Northern Tibet was a good indicator for global warming. The varied responses of community structure and biomass to the warming gradient indicated that moderate warming would promote the growth and development of plant communities, but fast temperature increasing would induce warming and drying environment, and less water availability for the ecosystem. Consequently, the productivity of plant community decreased, and the meadow ecosystem deteriorated.