Abstract: Ontology theories are applied to after-sale service of motor car in this paper. In modeling the problem, three ontology models are constructed, they are: ontology of driving behavior, ontology of driving environment, and ontology of automobile domain. With these models and their association, an ontology model for automotive after-sale service is built. Thus, the intrinsic factors affecting automotive after-sales service are clarified. Then, based on the model, a similarity calculation method for automotive after-sale service is put forward based on case-oriented reasoning.