Abstract: 1 . With an area of about 6,320,000 hectares and a volume of 14,360 million cubic meters, the forests in Xizhang form the third largest forest region of Our coun try.2 . The peculiarities of Xizhang’s forests consist in that (a) the forests are rich and ancient in species, the flora being young and connected with one another, (b) the horizontal location of the forests is concentrated and linked up and the perpendicular location is zonal and stratified, and (c) the forests have a long growth history and the biomass is tremendous, with the volume reaching 3,500-3,800 cubic meters per hectare somewhere.3 . The main laws of constitution and growth of the forests can be seen from the following facts:(a) Both component species and biomass of stands increase from northwest-north east to southeast-south, from high to low elevation, from river valleys to gorges of high mountains and from southern to northern slopes.(b) The number of vertical zones of forest rise from northwest-northeast to southeast-south; the limil of distribution of the forest is higher at northwest-northeast (4,300-4,400m) and lower at southeast-south (3,800-4,000m).(c) The order of the formation types of the forest is regular but not always so, depending on the ecological characteristics of the species and the water and temperature conditions.4 . The above-mentioned peculiarities and laws of constitution and growth of the forests in Xizhang come from the excellent habitat formed by the specific topography.