With the improvement of economic requirements and urgent need for transporting spent fuel assemblies, the research and development of spent fuel transport cask is important in China. The manufacturing precision of transport cask is a difficulty during the researching process, and variations in the manufacturing tolerances may affect the shielding safety of the cask. For the researching and developing ductile iron transport cask, deep blind holes are set in the cask cylinder to load neutron shielding rods. Considering the low manufacturing precision of deep blind holes by machining instruments, a sensitivity analysis of the effect of changes in manufacturing tolerance parameters on shielding is performed by using a Monte Carlo program. Taking the instruments manufacturing precision into consideration, the effects on shielding under offsetting the original position of the deep blind hole by 2 and 5 mm in the angular direction, by 5 mm inward as well as outward in the radial direction are analyzed in the report. Relative to the original dose rate, the dose rates caused by these parameters changes from −2.77 to −2.13% and are within the range of statistical errors, which shows that these parameter changes have little impact on the shielding and the manufacturing precision requirements of deep blind holes can be reduced due to the difficulty of manufacturing.