In order to implement“plug and play” automatic voltage control system（AVC）， it is necessary to expand common information model（CIM） for the purpose of standard integration between AVC and energy management system（EMS）. A voltage controller model is designed based on the analysis of current AVC systems， and the recursive composition method is adopted to describe the hierarchical control structure. With minor modification of the existing CIM， the voltage controller model is embedded into CIM by inheritance and association. Details of extended CIM designed for AVC is proposed.