Differences between plant biodiversity and grazing pastures grazed under improved management of rangeland habitat is of particular importance. The purpose of this study was to compare semi-steppe rangeland vegetation of Prdanan in the city of Piranshahr in the field under grazed and enclosed sites were considered. Sampled in both grazed and systematic random pastured five 40 meters transects were done in each study and a total of 40 plots per square were harvested. The results obtained indicate that in enclosed area, 44 species belonging to 35 genera and 14 families and in the grazed area 26 plant species belonging to 24 genera of 11 families were seen, and the greatest cover of the species in the enclosed area is related to the family of Poaceae and Asteraceae respectively with 11/34 and 64/13 percent and in the grazed area is related to the family of Asteraceae and Apiaceae with 74/30 and 08/23 percent. Uniformity and diversity of species richness and index of diversity using Shannon - Wiener, Simpson, alpha Fisher, McIntosh, and Margalef Mnhynyg was calculated by applying EstimateSWin 752, PAST AND BIO-DAP software. The results of the analysis of species richness in both areas claimed that the numerical richness, evenness and diversity of the enclosed area was greater than the under grazed area. The test results showed statistically significant differences between the two arenas by the Shannon index, and Margalef alpha Fisher.