Abstract: As the installed capacity of nuclear power steadily increases in China, nuclear power plants have to be faced with urgent requirements of participating in peak load regulation of power grid frequently; however the fixed refueling cycle length can hardly meet the economic operation requirements of nuclear power plants. Actually, the nuclear power plants are required to avoid reactor shutdown and overhaul during the electric peak consumption, especially in summer and winter. Multiple units overhaul simultaneously should also be avoided. In this way, a flexible cycle length is very important in nuclear power plants during normal operation. Although the cycle length can be adjusted by stretch-out operation or shutdown earlier than anticipated time, these methods will reduce the load factor of nuclear power plants, causing the waste of residual reactivity of fuel and the reduction of fuel economy. The purpose of this paper is to investigate the capability and feasibility of the flexible cycle refueling strategies of AP1000 nuclear power plant. According to this study, the ±1 months and ±2 months flexible refueling strategies were designed on the basis of AP1000 standard 18-month core loading scheme. The low leakage pattern was applied in the study for economics. Key safety criteria and fuel economics were evaluated for every pattern. By comparison, it is indicated that fuel utilization of the ±1 months and ±2 months refueling strategies is close to that of 18-month refueling strategy. Full-scope safety analysis is evaluated for every pattern, including core power capability verification, reactivity related accident analysis, radiation source and shielding calculation, nuclear process system evaluation, etc. The results show that the core design meets the requirements of safety criteria, and fully demonstrate safety and feasibility of the flexible refueling strategies. The study provides technical support for the flexible refueling cycle of AP1000 nuclear power plant. The flexible cycle refueling strategies can be widely applied in AP1000 nuclear power plant. The ±1 months flexible refueling strategies will be put into application in Haiyang nuclear power plant soon, which will make a good performance of steam extraction and heat supply.