Vegetation is found to be the most determinant factor affecting on natural ecosystems sustainability and equilibrium. Selecting suitable and compatible species for restoration of degraded lands serves as the main issue to rangelands biological reclamation and cope with soil erosion as well as desertification. Kermanshah province (west of Iran) is fraught with various forests and rangelands. Because of some climatic changes, pest outbreak, early and overgrazing, fire and etc., these natural resource are degrading increasingly which might be addressed as a desertification issue. The present research is aimed to identify most determinant factors on growth and distribution of dominant vegetation species in Kermanshah province. For this, first climate database consisted of 15 climate components from 26 stations located within and out of province associated to region vegetation were selected. Then, point data were converted to zone data according to interpolation and cell grid size methods so that data volume was reduced as per procrust coefficient and volume as Korzanofski method. Factorial analysis was used to reduce data volume as well as identification of most important factors. In addition, cluster analysis was used to zonation of homogenous areas. Next, area vegetation map was matched to factorial score map and factorial scores for 4 dominant species in forest and rangeland were determined. Results showed that, the most suitable method and cell grid size for interpolation of climate data are Kriging and 6 km respectively. Climate data were generalized to number of 622 points across the province. According to Korzanofski method, the best and most determinant factors on meteorological variables about 106 variables were selected. Factorial analysis indicate that four main factors involved temperature, precipitation, winter precipitation and wind reserved 47.9 , 23.7, 8.8, 6.7 respectively that accounted for about 87.168% of total. Kermanshah province was zoned into seven climatic area based on cluster analysis and factor score of four main factor : too hot and arid, too hot and semiarid, semi-cold humid, cold and semi-Mediterranean, Mediterranean semi-cold, and semiarid, windy cold and semiarid. Temperature was used as the main factor to nomination of abovementioned climatic area so that just in semi cold humid zone, precipitation played fundamental role. According to factor scores and primary parameters, Festuca ovina, forests, Bromos tomentellus and Hordeum bulbosa were evaluated suggesting that Festuca ovina had extended within two windy cold and semiarid and Mediterranean cold zones. Additionally it has more tolerant to precipitation and temperature, and developed under various precipitation regimes. Quercus species have higher temperature thresholds, as a result precipitation is the main factor controlling forest species extension in Kermanshah province followed by temperature. Bromus tomentelus had higher temperature tolerance threshold and it can be dominant under 500 mm annual precipitation. Precipitation factors is known to be the main factor affecting Hordeum bulbosa development followed by temperature. Keywords: Factor analysis, cluster analysis, Kermanshah, Kriging, Procrastes