Abstract: Reasoning algorithm based on polychromatic set theory for conceptual design of mechanical products is brought forward.An effectual solution evaluation algorithm for multiaim is used.With some concepts of analytic hierarchy process,fuzzy reasoning and neural network,the solution set with requirement satisfaction is evaluated and optimized,the optimum solution with requirement satisfaction is found.The application of this method is illustrated with an example of conceptual design for machining center of drilling,milling and boring,the solution set with requirement satisfaction is found.