To realize the management and reuse of the knowledge of straightness verification, the ontology theory is applied in the knowledge base system of straightness verification. The system is divided into three layers: domain layer, inference layer and application layer. The ontology of the straightness verification is established for formal description of the conceptions of straightness verification and the relationship among these conceptions. Related axioms, rules of straightness measurement are given out according to related standard documents. Finally, an application platform is provided for the digitized realization of the straightness verification.