Electric power equipment must be operated in the state of high reliability with its responsibility in the seamless power supply. Therefore, persistent maintenance is very important. There are many maintenance methods well known in industrial business. Among them, the reliability-centered maintenance (RCM) is a state of the art maintenance technique. This paper shows a RCM method for electric power equipments. This reliability-centered maintenance (RCM) has been applied in the fields of aerospace, nuclear power plants and rail system, etc. In this paper, we design the FMEA flow for power transformer and evaluate the importance level based on the fault information. The importance level is applied to the inspection period, fault detection method and operator selection. The results of the system are provided as a worksheet containing the information that needs to be maintained.