Festuca ovina is a perennial plant of the Graminae family that is a palatable and a highly productive species in rangelands and plays an important role for soil conservation. Due to the importance of roots for plant stability and soil conservation, in this research, the role of different treatments on the weight and length of plant underground organs were investigated. In each treatment (light grazing, moderate grazing, heavy grazing and no grazing), four 50 meter transects were randomly placed and 10 species were sampled on each transect using the nearest neighbor method. Overall, 160 plant species were sampled for experiment. After separating the aerial and ground organs and weighing their dry matters, data were analyzed to investigate the influence of grazing using ANOVA, tukey and Tstudent test in SPSSver16. Results showed that different intensities of grazing influenced the biomass of the aerial and ground parts of the plant. The result of the T test representing the height and weight of this plant in different grazing intensities had significant differences (P<0.01) with the height and weight of the aerial parts biomass. One way ANOVA showed that the weight of root between two grazing treatments of light grazing and no grazing and also between moderate grazing and heavy grazing did not have significant differences. Root length analysis showed that light grazing treatment did not have any significant difference with moderate but revealed a significant difference with heavy and no grazing treatment and the means were categorized in 3 groups (A, B and C).