Abstract: This paper presents a novel product layout modeling approach based on a hierarchical product layout element relationship net,and proposes a product layout polychromatic model for solving a mapping problem between product principle schemes and structural layout schemes.The hierarchical product layout element relationship net is constructed by using layout modules and attribute relationship net.Then the product layout polychromatic model and its reasoning algorithm are described with the mathematical representation of the hierarchical product layout element relationship net in polychromatic sets element pigmentation and unified color.Subsequently,the mapping process among product functions,motions and layout modules is formally described utilizing polychromatic sets boolean matrix reasoning rules.This representation supports axiomatic design of product layouts efficiently.Finally,NC machine tools layout design has been used to demonstrate the proposed product layout polychromatic model.