Large LNG storage tanks contain a large amount of low-temperature and inflammable and explosive LNG, which will cause great harm to surrounding people, property and atmospheric environment once leakage occurs.A three-dimensional numerical model was established for a large LNG storage tank at the LNG receiving station in the south,and the leakage and diffusion process of LNG was simulated.Then the influence of wind speed, wind direction and obstacles on the leakage and diffusion of LNG was analyzed.The results show that the wind has a stronger effect on mixed dilution of high concentration gas cloud,and a stronger effect on advection transport of low concentration gas cloud.Under low wind speed of 3m/s, the farthest downwind direction of gas cloud with 1/2 lower explosive limit can reach 554m.From downwind leakage to upwind leakage, the obstruction effect of the storage tank on gas cloud diffusion gradually increases,and the diffusion speed of gas cloud gradually slows down.The upwind leakage is the most unfavorable to the diffusion of gas cloud,and the most dangerous area is formed after stabilization.Obstacles will lead to the short-term accumulation of heavy gas cloud,and make the diffusion of gas cloud present two forms: climbing and diverging.By comparing the leakage and diffusion consequences of single tank and tank farm under the same environmental conditions,it is found that the volume of dangerous gas cloud in the tank farm at the same time is much larger than that of single tank.The main reason is that other large storage tanks in the tank farm hinder the gas cloud diffusion while changing the distribution of wind field,and extend the stagnation time of high concentration gas cloud.The research will provide reference for the prediction of the consequences of leakage and diffusion of large LNG tanks in the future, and serve as a basis for the formulation of emergency protection strategies.