In this study, a hybrid control method is proposed, in which both isolation bearings and an inertial mass damper (IMD) are used, to reduce the seismic response of a liquid storage tank. First, simplified models of the tank and IMD are illustrated. Next, to evaluate the effectiveness of the proposed method, three tanks, including a fixed tank, an isolated tank and an isolated tank with an IMD, are analyzed and compared. Last, parametric studies are conducted to investigate the effects of equivalent inertial mass and viscous damping of the IMD. It is observed that, compared with the fixed tank, the base shear of the isolated one is largely reduced, whereas the wave height is consequently amplified; for the isolated tank with an IMD, not only is the base shear more obviously reduced, but also the wave height is effectively controlled. What’s more, the base displacement of the isolated tank with an IMD is much lower than that of the isolated one. Therefore, the proposed method can be considered as an effective method to control the seismic response of the liquid storage tanks.