Abstract: Sustained forest management at two cases are discussed, namely ideal center and non-ideal center. For ideal center, the cut is near maximum current annual increment, so that we have got a mathematical model as follows: (1/1+exp[-(1/2)λΔt])-(1/1+exp[(1/2)λΔt]=1/1+exp[(-1/2)λΔt] Where, Δt—a cutting cycle; λ—intrinsic rate of increase; D—selection cutting intensity expressed. by selection cutting quantity/present biomass of stand, unit time For various cutting cycles, relation between λ and D are tabulated and plotted, respectively. For non-ideal center, the cutting age is away from maximum current annual increment than ideal center, and relation, between λ and D are given. Various cutting limits are also discussed. Under continuous selective cutting condition, the mathematical model may be shown as follows: dω/dt=λω(1-ω/w)-Dω Where, ω——biomass of stand in unit area; W——maximum biomass of stand in unit area which is allowed by environment (Carrying capacity). A analysis of this formula shows also that forest has certain selfregulating capability that can maintain stabe when total cutting intensity(D)is lower than λ. On the contrary, when D λ, forest has lost its self-regulating capability, so that the biomass of stand becomes less and finally, the system would be destroied.