Abstract: Aiming at the inefficiency and uncertainty of the artificial selection of cylindrical process dimension parameters of shaft parts and the difficulty of sharing and transmitting related process knowledge between heterogeneous CAPP systems, a method for automatically generating cylindrical process dimension parameters of shaft parts based on ontology is proposed. According to the process knowledge of design feature analysis, machining plan reasoning, process dimension parameter selection and other process knowledge involved in the process of generating cylindrical process dimension parameters of shaft parts, a knowledge representation model consisting of part structure layer, design feature layer, feature mapping layer and processing feature layer is constructed. The web ontology language OWL is used to represent the knowledge model ontology, and the meta-ontology model of the cylindrical process dimension parameters generation is constructed. The semantic web rule language SWRL is used to construct the inference rules related to the generation process of cylindrical process dimension parameters, and the automatic generation algorithm for cylindrical process dimension parameters is designed. The Jess inference engine is used to realize the automatic generation of cylindrical process dimension parameters, and the feasibility of the method is verified through an example.