Zagros ecosystem is considered as one of the most important biological sites in the Iran. This research was investigated in the Marivan region, northern Zagros forest, and western Iranian state of Kurdistan. In this study 120 circle sample plots (500 m2) were collected by random method in different aspect and altitude. In every sample plot the kind of species and number of trees and shrub were recorded. In the sample plots the micro plots of 5 m by 5 m (i.e. area of 25 m2) were designed and Herbaceous and shrub information was recorded then. Aspect, slope and altitude divided the four, three and three classes. Species diversity indexes including Shannon Wiener (H ׳), Simpson (1-D) and Margaleff (R1) were used to evaluate plant diversity in each sample plot. The means of different between diversity indexes in the aspect, slop and altitude class were estimated by ANOVA and DUNCAN test. Data analyzing was done by Past and Ecological Methodological software’s. Results showed the tree, shrub and herbaceous species belonged to 29 families and 80 species were identified in the study area. That Rosaceae and Fagaceae families have the highest number of woody species. Moreover, Compositae and Gramineae families were most abundant amongst herbaceous species. The increasing of altitude decreased species diversity. A significant different was observed for diversity index in aspect, slope and altitude classes. Therefore, in order by increasing of altitude the plant diversity decreased, higher of plant diversity observed in the northern aspect, 0– 30 percentage slope and 1400 to 1800 meter a.s.l. classes.
