Based on the characteristic feature parameterization and the superiority evaluation method (SEM) in extension engineering, a product-shape design method was proposed in this study. The first step of this method is to decompose the basic feature components of a product. After that, the morphological chart method is used to segregate the ideas so as to generate new product forms. Finally, the extension engineering method can be used to build the relationship between the feature parameters and the image vocabularies. With this method, designers are able to communicate with their clients via Internet and develop more suitable products for consumers by evaluating their impressions with the assistive system. It has been verified that this approach can reduce the development time as well as enhance the effectiveness and competitiveness of a new product.