To provide a theoretical and technical basis for base isolation of LNG storage tanks, based on the shear beam theory for the outer-concrete-tank and the velocity potential theory for the inner-steel tank, and by introducing isolation stiffness and damping, the equivalent mechanical model of LNG storage tank base isolation system was established, the movement equations of LNG storage tank base isolation system were derived according to Hamilton's principle and the theoretical expression of seismic response were given. To 160 000 m³ large LNG storage tank, the numerical analysis results showed that, in addition to wave height, the base shear and overturning moment damping effect was obvious, the foundation design of LNG storage tank was necessary to consider the impact of outer-tank, however, when designing the inner-steel tanks, the impact of outer-tank could be ignored. It was necessary to optimize the design considering the influence of isolation on the sloshing of base isolation of LNG storage tanks.