An intelligent CAD system for Involute cylindrical gear cutting tools is developed by VC++ and SQL server, and it includes four modules, such as user interface, instance query, intelligent gear tool design and database. The intelligent gear tool design is the key to the intelligent CAD system, and it is based on the forward reasoning production system, and as the Intelligent reasoning technology is used for gear tool design, a lots of expert knowledge could be made full use of. The design results by the developed intelligent CAD system are more reasonable than those by a traditional CAD system, and the efficiency and quality of the gear tool design also could be improved. The developed intelligent CAD system supports both 2D and 3D models, which can lay foundation for CAD/CAE/CAM integration of gear cutting tools.