This paper introduced the composition and classification of tree models,discussed the problem that branches and leaves with varying shapes be simulated by regulating their parameters.Then,we researched on how to use Iterated Function System(IFS) and billboard to simulate branches and leaves.Finally,by using this method,two classes of three-dimensional trees are simulated and applied to virtual scene.The results show that,three-dimensional trees simulated by this method have advantage of high vividness,diversity and real time response,which is valuable in 3D virtual scene simulation.