A novel common information model（CIM） data processing method for power system application software is proposed in the paper. CIM is applied to internal storage structure of a system with object-oriented modeling technique. CIM XML documents are interpreted using“pull” mode provided by NET Framework， and generated to C# CIM objects by reflection functionality. Network data storage， power flow calculation and so on， for application systems are realized by accessing and manipulating CIM objects directly.CIM processing package is developed with Visual Studio Team System 2008 development platform and Visual C# NET object-oriented programming language， and is applied to automatic voltage control（AVC） system which realizes loose coupling integration with energy management system（EMS）. This method has also reduced development costs of new system and improved the operating efficiency of the system.