Examination of relationships between plant communities with environmental factors is considered among the most important and complex issues related to natural resources and environmental management topics. In the present study, some of the most important environmental factors affecting growth and distribution of natural plant communities existed in Zanjanrood Watershed as well as their relations are discussed. For this purpose, the land use maps related to the years 1987, 1998, 2002 and 2009 were prepared using hybrid unsupervised method and the land cover density map was provided by means of NDVI. Subsequently, the diversity status of the plant species was determined in the area using alpha diversity indices. Information related to temperature and precipitation was obtained through statistics and meteorological data within a 60 year statistical period. Finally, using regression relationships and cluster analysis the role of each independent variable (environmental factors) on plant biodiversity was specified separately. The obtained results revealed a significant impressibility of plant communities by environmental factors during the years of the research. The highest correlation between environmental factors with tested vegetative characteristics is observed between elevation classes with vegetation types and density.