Abstract: In traditional CAD systems, the feature structures of parts are constructed interactively, where the maintenance of the original design intents and the formation of feature semantics are merely considered. In general, it is difficult to identify the source of semantics in interactive design systems. Here, we put forward a novel method that can automatically produce engineering richen part structure models according to function requirements and rules of sub-function combinations. In this method, an atomic function dependency graph (AFDG) is generated first according to the design requirements and the complete neighbor definitions of atomic functions in a pre-defined design rule library. The obtained AFDG is complete in a sense that each of its atomic functions has a compete neighbor in the graph. The completeness guarantees the validity of the generated structures. Then, a feature dependency graph (FDG) of a part is synthesized from the AFDG using pre-defined mappings between atomic functions and local feature structures. Finally, the FDG is transformed to a CSG-type feature structure model, which can be input to currently available commercial CAD systems to generate final CAD part models.