Flexible fuel management in a nuclear power plant relates to the operational efficiency of the whole plant, which not only satisfies flexible fuel demands, but also has a positive effect on environmental pollution control. The proposed management strategy aims at improving energy utilization rate of nuclear fuel in nuclear power plants, meeting the needs of peak electricity consumption in summer and nuclear energy heating in winter, enhancing the economic efficiency of nuclear power plants, and reducing carbon emissions, thus contributing to energy carbon neutrality. In this paper, the Core and System Integrated Engine for design and analysis (COSINE) nuclear design software package was adopted to study the fuel management strategy for alternate refueling in 68 groups and 60 groups of assemblies, based on the current 64 groups of refuel assemblies at Haiyang Nuclear Power Plant (NPP). The results show that the Haiyang NPP has the capability to refuel flexibly between 68 and 60 groups of assemblies, and the reactor core design meets the relevant design guidelines and requirements.