Abstract: Once a sodium leakage accident occurs in the main pipeline of the primary auxiliary system of a sodium cooled fast reactor, the leaked sodium will quickly burn, and the huge heat energy released by sodium combustion will instantly increase the temperature and pressure in the sodium process room where the accident occurred. Based on analysis of the domestic and international progress of mixed sodium fire accident research, this paper proposes the design of the pressure relief equipment for the mixed sodium fire. The study shows that the instantaneous high pressure formed during sodium leakage accidents can be effectively released to adjacent process chambers through pressure relief measures, and the combustion of sodium droplets brought into adjacent chambers with the pressure relief airflow will not make the pressure in the chamber building exceed its allowable limit. By simulating the design basis sodium leakage accident in the primary sodium process room, the performance of the sodium fire pressure relief device is verified, and the experience in operating the sodium fire safety protection system of the sodium cooled fast reactor is obtained.