Abstract:CASS is a general data of bidding. It has a good symbol system and being used widely in the editor of large scale topographic maps. CASS is developed on the basis of AutoCAD, so it has disadvantages of curve editor and revision of the eaves of buildings by the influence of the AutoCAD. However, Geoway has advantages of above aspects as a professional software for topographic maps editor, so it is urgent to develop a conversion program from Geoway to CASS. How to develop a conversion program from Geoway to CASS by Visual Basic language has been introduced in this paper.