A module partition method for product design was proposed. Firstly, fuzzy dendrogram clustering algorithm was used to illustrate the generating process of modules based on the correlativity analysis of function and structure between the sub-structures of product and then several module partition programs were obtained. Secondly, based on information entropy theory, mathematical evaluation model of module partition program for product design which considering the complexity of cross-series design, longitudinal series design and replacement design as the optimization goal was established, by which module partition programs obtained from fuzzy dendrogram clustering algorithm can be evaluated in order to get the most reasonable module division program. Lastly, straight-lead flower-line products machining equipment was used to illustrate the validity and rationality of the proposed method.