The work aims to study the fracture toughness of ductile cast iron for large-scale spent fuel transportation casks to give recommendations for evaluating fracture toughness in engineering applications. The fracture toughness data of specimens at different locations were obtained by conducting fracture toughness tests on top and nesting specimens. The two-parameter Weibull distribution and normal distribution were used for statistical analysis, respectively, to verify the applicability of the two distribution methods in the fracture toughness test, and to determine the satisfaction of the requirement parameters for low-temperature fracture toughness of ductile iron with large cross section. The fracture toughness data of ductile iron materials used in large-scale spent fuel transportation casks meet the requirements of Weibull distribution and normal distribution, and the fracture toughness of domestic containers was much higher than the international standards. The fracture toughness analysis and evaluation at ultimate service temperature have been completed and the fracture toughness has been systematically grasped, providing a basis for the structural design of vessels, material selection, failure mode analysis and defect assessment.