Abstract: This paper was written after the investigation al1 over the forest region in Sanjiangkou, Zhaotung, in May--August, 1973. In this paper the main object is the forest communities. The authors have discussed emphatically the problem on the ecological conditions, the nature, the present state, the succession of these forests, and the utilized direction for them, etc. They may provide a scientific basis for reasonable exploitation of the resources in these forests. All these will give reference materials to the related departments and units.