Abstract: As an important safety equipment in nuclear power plant,the emergency diesel generator（EDG） is mainly used to deal with the loss of offsite power accident. In order to ensure the reliability of EDG,the maintenance plan must be made,and the preventive maintenance must be carried out regularly. In view of the long maintenance time of the EDG,the unavailability caused by maintenance must be considered to bring additional safety risks,which becomes one of the important considerations for the quantity allocation of the EDG in HPR1000. According to the latest safety requirements,the function of removing heat of the fuel from the spent fuel storage facility is upgraded to the basic safety function. Compared with the domestic generation Ⅱ reactor,the HPR1000 takes into account the design basis conditions related to the spent fuel pool cooling,which made the 2×100% EDG configuration scheme difficult to find a proper EDG maintenance window. The main purpose of this paper is to analyze the maintenance window of the EDG in detail by using the deterministic and the probabilistic safety analysis methods, and find a new way to provide the allowable maintenance time for the EDG. The analysis results show that the allowable maintenance time of the EDG with 2×100% configuration can meet the actual needs of maintenance. Therefore,the HPR1000 can be maintained under the configuration scheme of two emergency diesel generators.