With the improvement of economic requirements of nuclear power operation, China General Nuclear Corporation (CGN) will gradually replace the more expensive primary neutron source assembly with the activated secondary neutron source assembly in the first cycle for reactor start-up. After activation, the secondary neutron source assembly needs to be adapted to the simulated fuel assemblies by underwater operation, and then integrated into a dedicated secondary neutron source assembly transport cask and transported to the reactor core. Therefore, the safety analysis for transportation of activated secondary neutron source assembly is important. Based on the NAC storage transport cask, the Monte Carlo program and CFX software are used for safety analysis mainly including structural evaluation, thermal evaluation and shielding evaluation. The result of structural evaluation shows that the containment is not breached under any of the normal conditions of transport or the hypothetical accident conditions. The result of thermal evaluation shows that the decay heat released by the activated secondary neutron source assembly can be derived effectively by the transport cask and the temperature of each component cannot exceed its corresponding limit. The shielding calculation results also meet the shielding acceptance criteria. Thus, this work verifies that the transportation of activated secondary neutron source assembly meets the design requirements in the main aspects of nuclear safety and is feasible.