Assessment of diversity and species richness in the understanding of ecosystem functions, protect and preserve genetic resources, evaluation and control of environmental change and the success or failure will help natural resource management programs. Arbitrary banning livestock grazing program and one of the most common and perhaps the most degraded pastures and reduced the diversity and species richness. Given the importance of livestock grazing on vegetation change in the qualitative and quantitative research to study the effect of the three grazed sites Reference area, Key area and Critical area on the diversity and richness species with different plant forms in southern slopes of Damavand mountain Summer Rangeland. Each unit, sampling was conducted along three transects 150 meters. Along each transect 15 plots with a scale and located within 10 meters of each plot type and number of plant species and the percentage and number of notes they were based. Numerical indicators to assess the diversity and richness of species diversity indices and using software Past Simpson, Shannon - Weiner index was calculated enrichment Menhnyk and Margalof. Data analyses was performed in SPSS18 software and compare the various indices of diversity and richness between regions with different intensities grazing Duncan's multiple range tests was performed.