Abstract: On the basis of research on functional feature model, including the main-body feature and interface feature, the conceptual design model based on cyclic mapping between demand region, function region and solution region is established. A formal representation method for the conceptual design and/or tree that is suitable for automatic solution is put forward and the solution algorithm is discussed. Finally a computer aided conceptual design automatic software system is introduced and the conceptual design of a woodworker is given as an example.