Abstract: The pre-cooling model of large-scale LNG storage tank is established, and the FLUENT software is used to simulate the pre-cooling process of the cryogenic gas in the storage tank. The change laws of the physical field during the cooling process and the inlet flow of the low temperature gas are studied. The results show that when the large-scale LNG storage tank is pre-cooled, the temperature of the gas is reduced first, and the bottom of the tank is cooled before the roof and wall; according to the requirements of the pre-cooling rate of the tank to regulate the flow rate of low temperature gas, the five-stage method of gradually cooled of LNG storage tank is proposed, and the inlet flow rate of different stages of low temperature gas is obtained.