This study was carried out in Sorkhdeh rangeland in Semnan province in order to determine the ecological species groups and their relationships with environmental factors as a tool for better management. Vegetation sampling was performed in 230 plots under equal random classification method and soil samples were taken in 0-15 depth. Climatic and topographic data were extracted by overlaying sampling locations maps on maps of topographic and climatic variables. In vegetation 15 sub-communities were identified using cluster analysis. Effect of environmental factors on vegetation sub-communities was determined using unbalanced ANOVA. Then environmental factors with significant effect were compared by Duncan method. Except percentage of relative moisture, total of studied environmental factors consist of EC, pH, CaCO3, Organic Carbon, P, N and percentage of clay, silt and sand, annual average of precipitation, annual average of temperature and annual average of relative humidity, aspect, slope and elevation had significant effect on vegetation. In total the studied environmental factors were able to distinguish the ecological species groups in the study area.