Abstract: For passive containment cooling system (PCS) of HPR1000, the one-dimensional natural circulation transient calculation code was developed based on drift flow model. The analysis of thermal hydraulic characteristic of PCS was conducted using this code. The change of flow rate, heat transfer coefficient, the temperature of heat exchanger inlet and outlet, air void and water level of the tank with different PCS heat transfer powers was obtained. The research in this work not only provides a reliable tool for evaluating the heat transfer capacity of HPR1000 PCS but also offers references for design and assessment of PCS cooling ability. And this work lays the foundation for the subsequent development of the code that can simulate the thermal hydraulic characteristic of a containment with PCS.