In order to solve the problem of semantic heterogeneity in data integration, this paper places emphasis on establishing a good data model in the stage of expressing data. Through the ontology modeling method on audit data integration, we using the method of top-down ontology integration, put forward to the process of building Audit-ontology. This paper constructs the audit domain ontology, defines audit information ontology Audit-ontology, and analyzes the concept and semantic analysis of the audit information,establishes ontology classification framework, and formalized expression by using OWL language. Finally, we connect the ontology to data source.