Nuclear criticality safety analysis is an important part of the design safety evaluation of radioactive material transportation containers. During the design of UO2 pellets transport container, criticality safety analysis shall be carried out, and the number of transportable packages shall be limited by the calculated criticality safety index (CSI), to ensure nuclear criticality safety under any credible scenario. In this paper, the Monte Carlo software SuperMC is used to verify the 49 benchmark test cases in 6 categories in the international criticality safety manual, and the maximum upper subcritical limit (USL) of this case is 0.919 74. Based on the test results of the transportation container under normal conditions and accident conditions, the maximum keff values of single package and package array under normal conditions and accident conditions are calculated. The calculation results show that the maximum keff value of single package is 0.28608, and the maximum keff value of infinite array package is 0.798 34. The maximum keff values of UO2 pellets transport container under normal transport conditions and transport accident conditions are both less than 0.919 74. The criticality safety index is 0 for those values are lower than the USL. The container design critical safety performance can ensure the critical safety during transportation.