Abstract: To meet the needs of CAD/CAPP concurrent designing in Computer Aided Concurrent Engineering, a kind of representation scheme for defining and operating form feature based on manufacture is presented in this paper. With an extension concept of "concave" for defining form feature, a method to represent form feature with "inner loops" is introduced. Parts are then designed with true"Feature- Based Design". The implementation of the physical data structure of B- rep solid model and form feature according to the representation scheme is presented and discussed. This scheme also provide enough message of part for CAPP system to analyze the manufacturability of parts and make the process planning automatically.