Abstract: The key issue of 3D geology modeling is the 3D data model.The data models involved in commercial systems as LYNX and Surpac mainly include 3D grid model,wire frame model,volume model,TIN(triangulated irregular networks) surface model and 2D grid surface model.On the basis of the characteristics of geological objects and the basic requirements for constructing geological model through the computer,the authors develop a new object-oriented 3D topologic data model based on component(volume element) for geology modeling.The geological objects are divided into four object classes:point,line,surface and volume.The volume class is further divided into four subclasses:composite volume,complex volume,simple volume and component.The component is the basic element of the division of geological volumes.It can be described by five object classes of point,feature link,arc,section polygon and component surface.We define twelve kinds of topologic relations between all these object classes.The detailed data structures of the object classes are also designed.In summary,the advantages of the object-oriented 3D topologic data model based on component for geology modeling are described as follows:1) The data model can be understood easily for the structural description of geological objects.2) The statistic analysis,the query,the visualization as well as the spatial analysis of geological objects can be conducted easily,and the common geometric boundary between geological objects need not to be digitized repeatedly.3) The geometric characterization of the component lends itself to efficient computation of volumes,and volumes of intersection between components.4) The definition of the three sections of component is of great advantage in the 2D geological interpretation,and the ability to extend and modify the boundaries in the third dimension satisfies the requirement for 3D geological interpretation.5) The ability to define the component plane at any appropriate location and orientation is also of great advantage in the modeling of irregular geological volumes.6) Using the data model we can model most of the geological objects.