Abstract: Choosing Hunan Province as the research object for its complex topography and well-developed geological structure and using SRTM DEM as the DEM data source, the authors, through data processing, projection conversion, MapGIS and ArcGIS data format conversion, and the superposition of the geological structure map of Hunan on the DEM, compiled the DEM 3D geological structure map of Hunan, realized the conversion of 2D geological structure map into 3D space. The resultant map not only keeps the professional nature but also shows three-dimensional effect and the sense of hierarchy through expressing the actual landform condition. In addition, it can reduce the time for reading the map and ensure the quality of interpreting the images. The results obtained by the authors have remarkable application value.