Abstract: Rapid product development and quick response manufacturing are the key issues to win competition in international market. Variant design is the key of rapid product development. Variant design refers to the techniques of adapting existing design specifications to satisfy new design goals and constraints. This paper applies the Product Dynamic Model to rapid product development. It presents a hybrid reasoning approach composed of case-based reasoning (CBR) and rule-based reasoning (RBR). It partitions the whole design process into conceptual variant design, assembly variant design and product definition variant design. At last, it describes the process of intelligent rapid product development based on Product Dynamic Model.