Abstract: Ecological species group were developed for hornbeam forest ecosystems in North of Iran that had been moderately disturbed. Species groups were determined from field observations and sample plot data arranged and analyzed in association tables. The groups were defined on the basis of species patterns of presence, absence and coverage values. Vegetation was sampled with randomized-systematic method. Vegetation data including density and cover percentage were estimated quantitatively within each quadrate and using the two-way indicator species analysis (TWINSPAN). The objectives of the study were to develop ecological species groups for lowland ecosystems types dominated by hornbeam in north of Iran, describe the site indicator values of species groups and increase our understanding of site-species relationships in moderately disturbed landscape in Khanikan lowland forests of Mazandaran province. Five vegetation groups were identified after the application of TWINSPAN programs. They are named after the characterizing species as follows: Menta aquatica (I), Oplismenus undulatifolius (II), Carex grioletia (III), Viola odarata (IV) and Rubus caesius (V). Result have showed that II, III vegetation groups and I, II vegetation groups had the most (65.5%) and the least (30%) of Sorenson similarity coefficient, respectively. Apparently, similarity coefficient of differentiated vegetation groups was high.