Abstract: This paper firstly proposes a Mamdani fuzzy inference system (FIS) model to simulate the relations among the quantity, quality and price of return products. Further, a benefit model of hybrid manufacturing/remanufacturing system is then developed, in which the demand linearly depends on the price, and the decision parameters include the price and the accepted quality of returns, the price of products, and the ratio of the quantity of manufactured products to the sold ones. Moreover, a modified niche particle swarm optimization algorithm (MNPSO) is proposed to search for the optimal solution of the benefit model. By applying chaotic map to generate the initial population and setting the thresholds of niche and particle, the searching space can be effectively enlarged and the diversity may be reserved. Finally, a numerical example illustrates the effectiveness of the proposed method.