This study is concerned with the vegetation investigation of Golestanak prohibited area, an ecotone with nearly 1800 ha area located between the timberline and subalpine-alpine zone in the central part of the Alborz Mountain Range (Mazandaran province). The effects of altitudinal gradient and aspect on plant diversity were evaluated by using CCA method (Canonical correspondence analysis) and a system of sixty sample plots were randomly used along five transects. The results showed that there is a negative correlation between the altitude and biodiversity variants meaning an increase in altitude leads to a decrease in the Shannon and Simpson indexes of the plots. The northern slopes have the highest plant diversity than the eastern and southern slopes, and the western slopes are allocated to the lowest plant diversity.