Rainfall after passes through the biomass and necromass, penetrates into the soil and make large qualitative changes because of rhizospher, microorganisms, horizon thickness and organic matter. This process is the result of atmospheric, hydrological and biogeochemical reactions influenced by seasons. In this study we investigated seasonal variations of base cation leaching (Ca²⁺, Mg²⁺, Na⁺ and K⁺) in the soil of mixed Hyrcanian beech located in district one of Shastkolate forest, Golestan province. Shallow and deep soil leachate samples (0-10 and 10-50cm) were taken within a year (2008/12/21 to 2009/12/21). Amount of base-cations of shallow and deep soil leaching in different seasons were compared by the one way variance and Duncan test. Results showed the amount of Ca²⁺, Na⁺ and Mg²⁺ contents of shallow soil leaching in seasons are different significantly (P<0.05) so that the most leaching of Sodium and Magnesium were observed in winter. Sodium and Magnesiumin deep soil leaching were different significantly (P<0.05) so that the most leaching of them were observed in winter and spring respectively. With the recognition of chemical properties variations of shallow and deep soil leaching, we can suggest that exploitation programs perform in February to make optimized biogeochemical cycle and maximized base cation leaching.