This study investigates 6(main kinds of) dominant species on Sejila Mountain in the southeast of Tibet.Statistics are gathered from 5 space factors,such as altitude,slope gradient,slope aspect,slope position and soil depth.The niche breadths of each dominant population on various spatial resources as well as the average weight(s) are calculated.Analysis and appraisal of the forest resources in this region are carried out on this base.The results show that in the virgin forest of Sejila mountain in Tibet,the sorting decrease of the niche breadth of the(main) dominant population can be listed as: Abies georgei var,Pinus densata,Picea likiangensis var.linzhiensis,Quercus aquifolioides,Sabina saltuaria,Pinus armandi.The niche metric space displays the major characteristics,which indicates that the forestry community is at a quite stable stage and equals to a climax community.