This paper describes case studies on workflow impact analyze with an enterprise ontology (EO). We build the EO with an ontology editor Proiege and integrate concepts of enterprise architecture and a process model into it to expand the EO. We use the expanded EO and Prolog query rules to analysis workflow dependency relations from the perspectives of routing, data and role. Through this, we analyze impact of changes in workflow process. Moreover, we have found the effectiveness of the EO and Proiege in modeling business management and, in particular, workflow representation and management.