Abstract: In order to verify the safety and reliability of the ice plug operation in the large-diameter pressure relief system pipeline of the third-generation nuclear power plant, the actual working conditions of the pipeline are simulated to carry out experiment al verification and analysis of the ice plug formation process. After repeated ice plug operations are evaluated, the experimental study on the damage of the pipe is carried out. The reliability verification process includes two parts: finite element simulation calculation, and physical and chemical tests. Based on the application of the ANSYS software, the temperature field of the pipeline during the formation of the ice plug in the pressure relief system of the nuclear power plant is simulated and calculated, and then the exact moment of the ice plug formation and the change of the thickness of the ice plug in a certain time domain are obtained to ensure the formation of the ice plug. Afterwards, it has a certain strength. The physical and chemical tests include microstructure examination, microhardness test, Charpy impact test, normal temperature tensile test, metallographic structure inspection, and scanning electron microscope fracture analysis. Based on the analysis of the above results, optimization su ggestions are made for the existing ice jam operation, and the ice jam operation procedure of the nuclear power plant is evaluated and improved.