Based on the basic knowledge of ontology and protégé, and the deficiency of semantic expression in the IEC61850 and IEC61970 Standard, this paper puts forward a mapping method from SCL to CIM, adopting Web Ontology Language OWL to build the semantic information model of SCL and CIM of substation knowledge ontology. In substation model, this mapping method could solve the problem of information sharing and interoperation between digitized substation and dispatch master station, and lay a foundation for further research on fusion of the two standards.