Based on the FMA structure decomposition of NC machine tool, the coupling and decoupling analysis of the relationships between the main motions were carried out by using the decision making trial and evaluation laboratory (DEMATEL), and the performance coupling matrix of main motions of components was obtained. An indirect mapping relation was introduced to replace the influence of the same generation coupling of main motions on the secondary motion layer; the information coupling degree and coupling variable degree were used to measure the indirect mapping and the direct mapping relationships respectively, and the fuzzy analytic hierarchy process(FAHP) was used to quantify them, thus estalishing the mapping transformation matrix between the main motions and the secondary motions performance, which in combination with the performance coupling matrix of main motions of components, completed the transfer of key quality characteristics in the function-motion layer. The validity and rationality of the mapping method are proved by the comparison of examples.