In this article we discuss the methods of 3d tree modeling by iteration function system ( ifs ) and l system based on the fractal . at the same time , we compare the two methods from the application of tree modeling in 3d cis and give the class definition of tree object from the object oriented point of view , in order that the tree object can be applied in 3d gis . all this research find a new and effective way for the visualization of tree in 3d gis 同時(shí),針對(duì)樹(shù)木實(shí)體在3dgis中的應(yīng)用,對(duì)兩種建模方法進(jìn)行比較,確定l系統(tǒng)是3dgis中構(gòu)建樹(shù)木實(shí)體的最佳方法,并從面向?qū)ο蠼嵌瘸霭l(fā),給出基于l系統(tǒng)的樹(shù)木實(shí)體類(lèi),從而使樹(shù)木實(shí)體作為3dgis中的對(duì)象之一融合到系統(tǒng)之中,為3dgis領(lǐng)域中關(guān)于樹(shù)木實(shí)體的表達(dá)尋找到一條新的而且是更有效的解決途徑。