An embedded software system based on energy management system（EMS） platform is designed and implemented with the“plug and play” method. The embedded system is divided into core module and interface module. The former is responsible for system strategies calculation， and the latter is responsible for data exchanging with EMS. The core module encapsulated can be applied to different EMS platforms. In order to ensure decoupling of core module and EMS platform，and let them change independently， the bridge mode is adopted for design and implementation of interface module. Each function interfaces can be implemented with standardization method， application programming interface（API） and agreement mode. The designed embedded automatic voltage control（AVC） system has been applied in several regional and provincial power grid control centers in China. Practice at site proved that this main station system can integrate advantages of EMS system in platform technology and AVC system in control algorithm，so that will improve practicality of AVC system greatly. The designed embedded system provides an effective way to EMS software integration for control center.