Abstract: Due to delays in the construction of nuclear power plant and insufficient fuel assembly storage space in the assembly manufacturing plant,the first fuel assemblies which cannot be delivered as scheduled are forced to be placed horizontally in the shipping container. Some fuel assemblies have been placed horizontally in the shipping container for more than one year. In view of whether the long-term horizontal placement of the fuel assembly in the shipping container will affect the mechanical characteristics of the grid spring,taking the AP1000 fuel assembly as an example,the mechanical characteristics of the grid spring are analyzed. The analysis shows that the long-term horizontal placement of the fuel assembly in the shipping container has little influence on the grid spring itself. When the fuel assembly is placed vertically,the grid spring can be completely restored to the original state in terms of mechanical characteristics.