In this study, the improved smoothed particle hydrodynamics(SPH)method was used to simulate the liquid sloshing in a prismatic tank under shaking excitation with different water depths and excitation frequencies. With this method, the roll-up and break-up of liquid caused by violent nonlinear sloshing can be simulated, and the simulation results were consistent with experimental data. Through changing the structure of the prismatic tank, the liquid sloshing in the prismatic tank with a baffle was simulated and the influence of the baffle on the liquid sloshing was analyzed. The results show that the water depth and the excitation frequency are the major factors influencing the characteristics of the liquid sloshing, and appropriately changing the structure of the tank can effectively suppress the liquid sloshing.