Abstract: Study on the process of the development of snag and its relationship to the abundance of hole-nesting birds in various forests in Xiao Xingan Ling Mountains shows that, as a part of forest ecosystem, full evaluation of the significance of snag should be made in forest management. Reserving snags with proper diameter and amount in the broad leaved-Korean Pine (Pinus koreaiensis), Spruce (Picea jezoensis and P. koraiensis) Fir (Abies holophylla and A. gracilis), and broad leaved-larch (Larix gmelini) forests is proposed.