The present invention discloses a passive decay heat removal system of a nuclear power station to supply electricity required for cooling the pump of still operate reliably. The invention consists of cooling the pump group suspended, stopped the cooling heat exchanger, turbine generators and the external heat exchanger group. Stop cooling the pump is mounted on a reactor coolant pipe to circulate the reactor coolant for cooling the reactor. Groups are still cooling heat exchanger is disposed between the reactor and stopping the cooling pump for the heat exchange between the supercritical fluid which is circulated through the reactor coolant and the supercritical fluid pipe. Turbine generator is connected groups still cooling heat exchanger, an cooling heat to stop the electric power generation by the supercritical fluid state in the last high-temperature gas is supplied to stop the cooling pump. External heat exchanger is mounted in the supercritical fluid pipe to the second to the last turbine generator cooling the supercritical fluid may send group still cooling heat. According to the present invention, the abnormal condition, for example, continue to advance and supplied stably by the electricity required for the still cooling pump even when all of the power loss of the supercritical fluid cycle to cool the reactor coolant of a nuclear reactor, the reactor It can significantly improve health. In addition, because the second critical pressure still cooling heat exchanger and the turbine generator, by fluid cycle it can be easily miniaturized and new nuclear power plants as well, the conventional effect of economically installed in a nuclear power plant.