Abstract: 【Objective】 To analyze the changes of plant community characteristics under long-term grazing conditions. 【Methods】 The species composition and quantitative characteristics of desert steppe with Stipa caucsica and Seriphidium borotalense on the northern slope of Tianshan Mountains were analyzed, so did the data from 1985 to 2001 by using the method of positioning continuous measurement. 【Results】 The results showed that the species composition and communities structure did not change, but the communities quantitative characteristics changed in a dynamic process during the 17 years. The height, coverage, and above-ground biomass of the plant community did not change more, and they changed the same way with natural precipitation from 1985 to 1995, so we could know that natural precipitation was the major factor affecting the changes of the community's quantitative characteristics, followed by the grazing factor. But the changes of the communities quantitative characteristics had a fluctuation greatly during the period from 1996 to 2001, whether it was the influence on climate or the role of grazing pressure that would be studied in the future. 【Conclusion】 In the period from 1985 to 1995, the fluctuation range of the height, coverage and above-ground biomass of grassland community was small, which was basically consistent with the fluctuation law of precipitation. The main factor affecting the change of grassland community quantitative characteristics was precipitation. Grazing disturbance is a secondary cause;During the period from 1996 to 2001, the quantitative characteristics of grassland communities fluctuated more than before,and whether it is the effect of climate or grazing pressure needs to be further studied.The results can provide data basis for the rational grassland utilization strategy.