This paper puts forward a multiplatform identification method to overcome the limitations of a single platform strategy when mass customization is required. The method is applied to redesign or consolidate an existing product family. The method consists of four steps: (1) the determination of component values, (2) the estimation of component redesign efforts, (3) the platform component identification, and (4) the formation of multiple platform instances. An ontology-based framework is also provided to facilitate the information representation and the data integration in the identification of multiplatform structure. Once the platforms are identified, an ontology reasoning mechanism verifies the platform sharing among products and determines the possible multiplatform coalition. A water cooler product family is used to illustrate the ontology-based multiplatform identification method.