Abstract: This paper discusses the difficulties of the loading operation process for the annual refueling core of M310 improved nuclear power unit, and studies the arrangement of the annual refueling core, the deformation form of the fuel assembly and the loading measures of the M310 improved nuclear power unit. Taking the loading operation scheme of the second overhaul core  of Unit 1 of Fuqing Nuclear Power Plant as an example, based on the analysis and loading assumptions of the deformation characteristics of the fuel assemblys, the existing "snake" loading method is analyzed in depth and an optimization improvement scheme for correcting the loading order of the last three rows of fuel assemblies is proposed. After the verification, the optimized annual refueling core loading operation scheme is feasible, which can significantly improve the safety and efficiency of the loading operation.