Abstract: Refueling for the reactor core is a top priority for a nuclear power plant unit in the course of yearly refueling overhaul.Taking the fuel loading diagram for the 3rd cycle of No.1 and No.2 unit of Tianwan NPP as an example,this paper introduces the operation process for three refueling methods,i.e.,the all-in out,the shifting within core and chainre fueling.Time efficiency for these three refueling methods is estimated,and the advantages and applicable scenarios for these three refueling methods are analyzed and compared.The actual refueling operation for Tianwan NPP verified that the latter two refueling methods are feasible,and can greatly improve the efficiency of refueling.