Abstract:Determining the cutting age classes at each cutting time for maximum economic benifit of a planted forest within a planted period can be cosidered as an optimal control problem of an discrete system. According to the timber price, tending cost,reforestation cost, interest rate of bank, as well as the changes of these economic indexes during the whole planning period, each optimal cutting age can be ditermined by appling maximum principle, and the influence of these indexes on the cuttong ages can be also analysed.