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This study was carried out to investigate the effect of ecological and geomorphological factors on establishment of plant communities in Chenar Rahdar region of Fars province, with an area of 31,790 hectares. The studies of physiography, climatology, geology, lithology, geom.orphology, and phytosociology were conducted. Using aerial photographs as well as slope, aspect, altitude, lithology, and geomorphology maps, uniform work units were determined. Considering BraunBlanquet-Kuchler method (Floristic-physiognomic method), separation and classification of plant communities were done in each uniform work unit. According to some vegetative characteristics such as storey, density, and life form and then using color patterns and numbers each plant unit was shown on the vegetation map with its physiognomic formula being defined. Results showed that the plant communities established in the mountain unit, were mainly affected by climate while in hills and high grounds, soil was the effective factor. In those parts of the study region where degradation was lower, there was a close relation between the geomorphological faces and plant communities. On the homogenous geologic formations, the variety of plant communities depended on the elevation while population was influenced by slope and aspect. Among different soil characteristics, texture, depth of horizons, sand hardpan, and the amount of gypsum and lime played the most important role in determining the plant communities.