The modularization design CAD system of CNC gear form grinding machine was developed by combining CAD with modularization technology. According to the design principles of modularization, the modules of gear form grinding machine were divided on the basis of function analysis. Taking UG software as the developing platform, the parametric 3-D modeling module bank and a database were set up. Under the guiding of the system interface, users could complete such tasks as module choice, module combination, and calculation etc. Therefore, computer aided modularization design of CNC gear form grinding machine could be realized.