To quickly find the changes in two 3-D CAD model files and enhance the efficiency and security of transmission in the CAD collaborative design system, a method to compare and analyze the differences of 3-D CAD model files is proposed. First, the feather information of CAD files was extracted using APIs of CAD software and stored in the neutral feature file. Then, analyzing and comparing the feature file, the information about adding, updating and deleting was obtained by the given algorithm. Finally, the information was rendered and showed to users in a readable method. The application in Catia validated that the proposed method is feasible and valuable in engineering.