The structure of a bridge symmetrical model（BSM） is proposed to unify the power system equipment databases of the operation management system（OMS） and production management system（PMS）. The decoupling of the logic and physical equipment， the bridge link of logic and physical equipment and the crucial effect of the operation position and abstract physical equipment in unifying OMS and PMS equipment databases are discussed. Through the bridge in the BSM， the specific equipment classes can be symmetrically and independently derived in OMS and PMS by the inheritance technique to meet the different equipment management requirements. In addition to using the BSM as the unified equipment database structure of OMS and PMS， BSM can also be used to realize the integration of the two equipment databases.