Abstract: The difference of vapor cloud density and the variation of atmospheric turbulence caused by ambient temperature are the main factors influencing the leakage and diffusion of LNG. Hence, it is very necessary to study the influence of the variation of ambient temperature on the diffusion rules of LNG. With the component transport model and the Realizable k-ε turbulence model in Fluent software, a numerical model of vapor diffusion caused by the surface leakage of LNG was established to explore the influence of ambient temperature on the volume fraction distribution of methane, vapor cloud density and atmospheric turbulence intensity in the process of LNG leakage and diffusion. The results show that under the low ambient temperature, the volume fraction lines of methane in the LNG vapor cloud is in the shape of"sawtooth", resulting in the increase of the horizontal diffusion range of the Low Flammability Limit (LFL) and 1/2 LFL of the methane, while under the high ambient temperature, the maximum range of diffusion of methane at LFL is 115 m farther than that under the low ambient temperature which leads to the increase of the diffusion range of methane at 1/2 LFL in the horizontal downwind direction. In addition, the increment of the turbulence intensity increases with the rise of the temperature in the area where the volume fraction of methane is greater than 1/2 LFL, while it decreases with the rise of temperature in the area where the volume fraction is less than 1/2 LFL. In the range of 100-200 m around the source of leakage, the increment of the turbulence intensity resulted by "temperature inversion" can be up to 0.79 times. The research results could provide references for prediction on leakage region, safety storage and transportation and emergency rescue of LNG.