Abstract: The present invention relates to a metamodeling unification system, in particular to a system for metamodeling unification to guarantee interoperability between an UML model of IEC 61850 and an UML model of IEC 61970. According to the invention, all IEC 61970 smart grid application using IEC 61850 data source easily obtains interoperability between applications and actively react to change of international standard because application developers use data by referring to a single UML IEC 61850/61970 unified model and refer to a single UML model reflecting flexibly constant modification of IEC standard, if any.