Abstract: The output about product information in available CAD software is a static description for a sequence of features．The relationship of features has been overlooked．Actually features must follow a definite rule when they are assembled in to a part．This paper discusses the main limitation of the transition feature approach in product model．A new definition of transition features and the relationship among them are discussed．Based on the relationship matrix of transition features and its non-looped digraph，an approach to product modeling is presented．Finally a typical part is used as an example to test the applicability of the approach．