In this paper we analyzed the product design process model based on function-principle-structure. Regarding the existing products as an object for module partition, we researched the related principles and quantitative method based on the function, principle, structure between the two parts. In the research of structural-relation, the structure related principles and quantitative method based on the assembly relation were proposed. We constructed the correlation sub-matrix for function,

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... e and structure, weighted the correlation sub-matrix and generated comprehensive correlation matrix; According to the comprehensive correlation matrix, we calculated the maximum correlation between parts. With average correlation for threshold, we proposed product module partition methods and steps based on clustering analysis, and realized product module. Finally, we use the case of speed reducer to verify the effectiveness of the module partition method.