In this numerical study, a 2D rectangular tank under horizontal excitations, is used to analyze the variation of sloshing impact pressure by baffle ratio variation. The tank is fitted with horizontal baffles on the walls, in order to use the air-trapping effect between the baffles. The Reynolds-Averaged Navier-Stokes (RANS) model with Volume of Fluid (VOF) equation is adopted to perform the sloshing phenomena. In order to analyze the effects of baffle length and gap, the Baffle ratio(BR) is considered. The results show that a lower baffle ratio of 0.5 had the most slosh reduction rate. In particular, 14.2% and 56.6% sloshing impact pressure reduction rate were reported for BR 0.5 cases.