Abstract: Hyrcanian forests are located at green strip extending over the Northern Slopes of Alborz range of mountains and the Southern coasts of the Caspian Sea. In order to study Caucasian walnut in the Hyrcanian forests in Nowshahr, North of Iran, two sites were selected. Within Behsara site 8 and within Larochal site 23 circular plots with an area of 0.1 ha were established. Qualitative and quantitative characteristics were evaluated. Soil and climate condition were performed too. The results indicated that Caucasian walnut extends in special environmental conditions. This species is distributed in flat sites in the riversides. The results showed that Caucasian walnut grows in semi-deep to shallow soils with medium nutrient requirement. In the most sites, the soil texture is clay-silt and clay-sandy and pH varies between poor acidic to alkaline. The mean annual precipitation was 1300 mm and the mean annual temperature was 11°C. The mean density was 101 stem numbers per ha. The mean diameter at breast height was 49.7 cm and the mean crown diameter was 9 m and the mean total height was 28.9 m. In this study, 17% of the tree's trunks were non-cylindrical, 20% were bi-branch, 16% were without branches and 9% were non-symmetric crowns. The regeneration of Caucasian walnut is established every year. The others species in the study sites consist of Carpinus betulus L., Alnus subcordata C.A.M., Quercus castanefolia C.A.M., Acer velutinum Boiss and Diospyrus lotus L. The distribution of maple tree and alder tree is more frequent than others.