Abstract: 【Objective】 Study on Community Dynamics of Iris ruthenica Ker.-Gawl. Meadow in the Middle of the Northern Slope of the Tianshan Mountains. 【Method】 The plant species composition and quantitative characteristics of the community under grazing conditions were analyzed from 1985 to 2004 by a continuous positioning method. 【Result】 The results showed that the community pattern of the species composition had not changed, Iris ruthenica Ker.-Gawl. always occupied the position of the dominant species, Geranium pretense, Poa pratensis and Helictrichon were always associated species in the past 20 years. The height, coverage and aboveground biomass of community were still some fluctuation state. and sometimes there would be some significant differences between inter-annual, it could be more than 2 times between the maximum and minimum amplitude, but the growth and decline of the community were all reversible. The coverage and the aboveground biomass of Iris ruthenica Ker.-Gawl in the community increased with the time growth, so the grassland was degraded from the perspective of grassland utilization. 【Conclusion】 The dominance of Iris purpurea in the study area is gradually increasing, and the grassland is developing in a degraded direction. The main cause of community fluctuation is climatic factors.