Abstract: To effectively evaluate the vibration safety of large unanchored vertical liquid storage tanks, a finite element model was established using the ADINA software, considering fluid-structure coupling and contact effect. The dynamic response of the tanks under the effect of horizontal seismic wave and the coeffect of horizontal and vertical seismic waves was studied. The results show that vertical seismic stimulation has a smaller effect on the horizontal displacement and stress of the tank wall compared with horizontal seismic stimulation. According to the distribution of the displacement of the tank wall along height direction, it can be learned that the lower part of the wall deformed more greatly under seismic stimulation. By obtaining the maximum equivalent stress distribution of the tank wall, it can be learned that the equivalent stress is mainly determined by the circumferential stress. The research results lay a theoretical foundation for the safety evaluation of large unanchored vertical liquid storage tanks.