In this paper, FME software platform for the conversion to digital city map, for example, the first of the DLG data analysis, and the corresponding pre-processing work to do, and then design the corresponding CAD data to GIS data conversion layer, and follow the attribute relationships design principles, to establish properties of each model's spatial database table. Finally, through the design of conversion programs to create conversion flow charts, design conversion process and add the appropriate transform function, and ultimately build a CAD-DWG data to GIS lossless conversion of the GDB data model. This total conversion model to build eight, respectively, elevation point conversion model, the control point conversion model, the water conversion model, residential conversion model, traffic conversion model, vegetation conversion model, the feature sub-layer switching model, there is an auxiliary class then the edge of the framing table conversion model, the successful conversion of the two data. The results show that the experimental realization of the basic DWG CAD data to GIS for the GDB data attribute information of spatial information and fast, lossless conversion, the conversion results are basically no attribute information is lost, the map data sharing provides a viable solution.