Abstract: Presents a methodology to plan the reuse strategies of common modules in a product family using concepts of function degradation, reliability, function requirement, cost and life time. A Markov chain model is employed to predict function degradation and reliability, in which utility model is used to evaluate the preference between used and new modules. According to the analysis, used modules satisfy the requirement of the next product series and reduce the total cost. By applying the proposed model in a case study of refrigeration system of refrigerators, the paper demonstrates advantages and general adaptability of Markov chain in the design of the reusability of common modules in a product family.