Abstract: The computer simulation to the system on forest resources is an important method to realize the forest resource management.Using a mathematical model of tree diameter distribution in forest system level,this paper develops the corresponding application software of forest system simulation with Visual C++.With the national continuous forest inventory data of certain area in Chengde City,Zhangjiakou Mountain Area of Hebei Province,it verifies that the diameter distribution model and the related technical methods are correct.Meanwhile,the experimental results show the significance of the model for forest resource management and a very wide range of application.