Abstract: Fieldbus technology iswildly app lied in electrical control system ( FECS) of power p lant by its easy operationality, dispersivity, reliability, accuracy, openness, efficiency and easy to maintain. App lication of electri2 cal control system based on fieldbus in large scale power p lant is introduced. The detail analysis is given aiming at the real time character and reliability of different parts, and the results indicate that the designed FECS is able to satisfy the reliable request of the power p lant electricity control system.