Abstract: The General Stand-Age Transition Equations (GSATE) are set up in this paper. GSATE is a dynamical model of a forest in a large area. This model can deal with clear cutting, selection cutting, tending, planting and regeneration, and predict the consequence of the operations above mentioned. The prognosis programs have been made out, that associate with the timber resource of our country.The model GSATE is able to use for the prognosis of forests in another scales.