From figures of cut standard trees and by the appropriate data processing methods, research has identified biomass ratio for body parts, branches, leaves and roots of trees in the Northern mountainous region as respectively: 70.5 percent, 11.5 percent, 4.0 percent and 14.0 percent. The equation Wl=0.1080*D2.1234*H0.3598 was chosen as biomass equation for above ground parts of the trees
biomass for underground parts of the trees was calculated from the above ground biomass according to the equation W2= 0.1750* (Wl)O.9823
the equation W=0.1080*D2.1234*H0.3598+ 0.1750*(0.1080*D2.1234*H0.35911)0.9823 was chosen as general biomass equation for the natural forest in the Northern mountainous region. Carbon coefficient 1\,=0.45 was used for conversion of dry biomass into carbon volume of timber trees in natural forest in Vietnam.