Many problems would be induced by the change in LNG tank temperature or components.Such as the stratification and rollover phenomena in large-scale LNG container，and the evaporation in closed small-scale container，etc.A mathematical model for LNG stratification and rollover under the condition of disturbed flow is established based on the equation of viscous fluid.Through numerical simulation，the developing processes of LNG stratification and rollover can be visually observed.The numerical simulation results revealed that the stratification of LNG is the basic reason for the rollover phenomenon，and the flow of thermal boundary layer inside the LNG tank is the direct cause for the rollover of the LNG stratification.By virtue of the disturbed flow model，various factors which affect the rollover phenomenon were analyzed.When the heat leakage is greater than 30 W·m-2，the changes in heat leakage value has little effect on the rollover time.When the tank is 70% full，the rollover happening takes longer time as the container volume increases.The measures for preventing LNG stratification are proposed.