Product design planning is typically carried out by assessments on product functions by considering customer demands. The connection between product series is an important factor which affects consumers’ subjective  perception. To optimise a product design, the structural relationship between product functions was determined in this study by the DEMATEL method so as to weigh the market connections and the importance of a product’s influence. The analytic network process (ANP) method was also use to create product designs based on the market segmentation consideration. The mutual relationship obtained from the modularization during the development process of new product designs can be combined with the new product features obtained from the systematic grouping methods. Based on the results of the case study, the capability of developing innovative product series can be enhanced