According to the principles and key technologies of the 3D CAD modeling and data conversion between CAD and Arc GIS, combining with the characteristics of different geographical entities, this paper classified the methods of 3D modeling. And then, the paper obtained the best method of model simplification and the optimal method of data conversion, which was facilitating to further processing and analysis. This method made the3 D CAD model fully presenting under the Arc GIS platform by storing the DWG files ...