Plant functional traits reflect the response and adaptation of plants to the growth environment, linking the environment, plant individuals and ecosystem structures, processes and functions. Grazing as the main land use of grassland ecosystems, play an important role in community structure of grassland ecosystems and changes in ecosystem functions. In this study, the functional traits of Stipa breviflore were studied under different grazing intensities of Siziwang banner, Inner Mongolia. Meanwhile the effects of grazing on grassland community structure were discussed. The results showed that: (1) with the increase of grazing intensity, the traits, individual biomass, plant height and breadth of crown were significantly smaller and shorter. (2) Through the trait plasticity change spectrum, we found that the plasticity indices of the functional traits were the highest in the heavy grazing area and the lowest in the light grazing area. The plasticity responses of stem mass, leaf mass, biomass of whole plant to grazing were the sensitive, but that of stem base diameter, crown and leaf mass were inert. (3) The variability of plant functional traits increased with grazing response intensity, the coefficient of variation (CV) and response degree (PI) of S. breviflora were consistent with the exponential equation y=0.08+0.18e^1.61x (R²=0.53, P＜0.05), the variability of plant functional traits and the response intensity of traits to grazing were proportional. (4) Among the factors affecting aboveground biomass, phenotypic functional traits including width of clump crown, average leaf length, leave number and total leaf area contribute to 72.93%. With the increase of grazing intensity, the variability of S. breviflora increased, and the plasticity was enhanced, which provided a mechanical explanation for the reason why Stipa breviflora is still a constructive species under the conditions of longterm grazing.