Abstract: In order to study the seismic response of liquid storage tank under bidirectional seismic excitation, the 15×10⁴ m³ vertical unanchored liquid storage tank was taken as the object, and numerical analysis on seismic response of vertical unanchored tank was conducted with the finite element software ADINA, considering the contact nonlinear. The whole system was mainly divided into two parts, i.e., the basic isolation components and the liquid-structure interaction subsystem. The structure and liquid region of the tank were simulated with the shell element and potential fluid element respectively, and the three-dimensional isolation was equivalently replaced by a spring-damping system. Subsequently, analysis of uplift response, acceleration time history, liquid sloshing height, wall stress change, base shear and overturning moment was carried out for the liquid storage tank with Bathe integration method. The results show that: under the excitation of El-Centro seismic wave, the tank bottom is uplifted before seismic isolation and the uplift area is in the shape of "crescent", which disappears after seismic isolation. Installing a seismic isolation layer in the liquid storage tank could effectively reduce the dynamic response such as acceleration, wall stress, base shear force and overturning moment. However, liquid sloshing height of the liquid storage tank after seismic isolation increases. The research results could provide reference for the seismic isolation design of liquid storage tank.