The distribution and activities of the microorganisms and the dynamic variation of the biochemical processes of the soils under different communities of Pinus koraiensis were studied and revealed the following results: 1. The abundance of microorganisms and the intensiveness of biochemical activities of the litters and soils differed markedly among the three forest types. The general tendency was that both were high in Tilieto-Pinetum, comparatively low in Betuleto-Pinetum,and least in Querceto-Pinetum. 2. The total number of microorganisms, the number of different groups of microorganisms, and the activities of the enzymes of the litters were higher than that of the corresponding soils. 3. The average annual activities of the hydrolytic enzymes in litters under Tilietoinetum,were higher than that of Betrrleto-Pinetum and Querceto-Pinetum, while the total activities of the oxidative enzymes in Tilieto-Pinetum and Betuleto-Pinetum were more intensive than those in the Querceto-Pinetum.