The model for the leakage and diffusion of liquid ammonia tank established using the species transport and reaction module of Fluent in order to investigate the leakage of liquid ammonia due to storage tank failure. The corresponding influencing laws were obtained by changing the height of leakage source and the size of leakage aperture in the simulation. The potential hazard of liquid ammonia reserved at temperature and high pressure or low temperature and low pressure condition was obtained by comparison of simulation results. The results show that the high concentration of gas diffusion on the leeward side will increase with decreasing height of leakage source, the leakage rate of Ammonia tank and the concentration of gas diffusion on the same location increase as the size of leakage aperture increase, the distance and hazards of gas diffusion during the same time will increase with increasing when using storage mode of normal temperature and high pressure under the same leakage condition.