An intelligent 3D fixture design method, which can solve interference problems between each workpiece, tool and fixture module to design optimal types, specifications and layouts of the fixture system. The design method of the present invention is based on a parametric solid model of 3D CAD software, which uses a space vector to determine if interference exists, and the interference position of such, between the solid models of workpieces, tools and fixture modules, and further utilizes a genetic algorithm to search type and its design shape and position parameters of each fixture modules, to design an optimal fixture system and related specification and layout.