Abstract: Once leakage happens at a large-scale LNG storage tank, it will threaten personal and property security seriously around it. The domestic and foreign research progress related to LNG leakage and diffusion was described from the aspects of theory, experiment and numerical simulation based on the sufficient investigation, and especially breakthrough research achievements on the numerical simulation in recent years were expounded. It is shown that the theoretical models for the gas diffusion formed after the leakage of large-scale LNG storage tank mainly include Gauss model, phenomenological model, box and similarity model, and shallow model. LNG leakage experiments provide a great number of basic data, including meteorological parameters, gas cloud and liquid pool combustion. And in term of numerical simulation, extensive researches are carried out on the diffusion of LNG leakage gas cloud, and particularly the evolution process of LNG leakage diffusion, the morphological change of gas cloud, the influential area and the explosion range are simulated and analyzed under the coupling effect of different influential factors. Then, three kinds of methods were comparatively analyzed. It is indicated that numerical simulation method is advantageous with low cost, high accuracy and strong operability, and it can not only expand theoretical and experimental research results effectively, but also be used to study the LNG leakage diffusion under complex working conditions. The research trends of the 3 methods were predicted. It is suggested that the research on leakage and diffusion of large-scale LNG storage tank at home and abroad needs to be combined with the actual situation. Future research should use numerical simulation as a dominant method, and experimental and theoretical research as an auxiliary one.