Abstract: The inhabitability of the main control room during accident situations and control of radioactivity release are related to the performance of the nuclear air cleaning system of nuclear power plant,their operation reliability is affected by the leak-tightness of ductworks,performance of iodine absorbers and HEPA filters,control strategy of electrical heaters,correctness of the fire detection system and so on. Some studies on related aspects are carried out and improving strategies are addressed in this paper for enhancing the operation reliability of the nuclear air cleaning system of nuclear power plant.