Abstract: To maintain containment’s integrity in the accident when spray system isn’t available, a design of passive containment cooling system (PCCS) was presented. Using one-dimensional homogeneous equilibrium method, the model of PCCS natural circulation loop was established, and the one-node two-composition model for containment was also created. The numerical models were solved by Newton iteration method. The steady-state characteristics and the transient behaviors of PCCS as well as containment under the LOCA scenario were investigated. The results show that the energy in the containment can be effectively removed by PCCS in a period of time without spray system. However, the tank water should be refilled and cooled for further decease of containment temperature for the long run.