Traditional conceptual design methods cannot express designers intent directly because of the lacking of 3D interface mechanisms. Conceptual design based on virtual prototype can not only provide a 3D virtual design environment, but also meet the needs of low costs, short cycle and flexibility of modern design. Considering the characteristics of conceptual design and the feature classification of virtual prototype, a novel virtual prototype-based product model V-desModel in conceptual design is presented in this paper.It introduces virtual feature concept in product's view models,and employs expandable 3D entity-constraint graph to describe the constraints between design objects.V-desModel can effectively support the process of cooperative design and concurrent design.By employing the concept of virtual feature and method of virtual feature generation,V-desModel can solve the insufficient information problems in constructing virtual prototype during the conceptual design of product.It can not only expangd the means and ranges of conceptual design,but also be beneficial for the exertion of creativtity during conceptual design.