Based on Udvardy system of classification in world network maps of biosphere reserves of 1995, the situation of the Miankaleh biosphere reserve of Iran, located in the southern coast of the Caspian Sea, was expressed as rainy and temperate forests and semitropical, whereas in 1975 he called it as mixed mountainous biome system. As the Udvardy classification, in large scale, is for national and regional use, it may not be able to separate the various kinds of existing habitats in a Biogeographical Province. T test the Udvardy classification theory and to investigate its probable disorder in it, by recognition of flora, the vegetation of the reserve has been ecologically studied. In the present research, the cluster analysis for classification of plant community and the ordination method for analysis of environmental (water table level and electrical conductivity of soil and water) relationship with plant communities have been used. The flora of the region, with over 200 species, with the origin of Euro- Siberian and Irano- Touranian, have been recognized and the presence of plant communities have been related to water table level and salinity of soil and water. Over 90 percent of plant species are annual grass type and permanent which are for non-mountaneous and proof of the second theory. It should be noticed that formation of plant communities of Miankaleh is more affected by water table and salinities of water and soil. This means coastal and waterlogging regimes prevail. In relation to Udvardy theory it seems that, based on the existing and paleoecological documents of 1905, the place of the biosphere reserve of Miankaleh, as a unit, was a rainy forests biome. Before fragmentation of Miankaleh winter and Elborz mountainous habitats, due to the urban developments, in the present time, determination of the situation of Miankaleh reserve is difficult due to climatic -ecological changes.