Abstract: Great research progress has been made these years in the sloshing suppression in liquid tanks using perforated horizontal or vertical plates. Perforated boxes installed at tank side walls are proposed for sloshing suppression in liquid tanks, integrating the merits of both perforated horizontal and vertical plates. Then, the suppression effect of the perforated boxes with different porosity and pore shapes under the condition of different shaking frequencies of external excitations is analyzed using physical experiments. By analyzing the measured surface elevations and the captured pictures, it is found that the existing of performed boxes can increase the resistance of liquid, induce wave breaking and then generate aerated flow with vortices, which can inhibit the increase of sloshing liquid. However, the porosity and the pore shapes have negligible effect on the sloshing suppression. It is also found by using wavelet transform that, the reducing sloshing amplitudes for the natural frequency components at the first and the second of the tank is the main suppression mechanism.