Based on the physical modeling experiment,we study the main factors effecting the horizontal wave pressure of the penetrated breakwater with both-sides baffles and their regularities under the irregular wave.Without the overtopping wave,we carry out systematic physical model experiments respectively for the three kinds of structures,i.e.the structure without hole baffle,the one with staggered hole baffle and the one with unstaggered hole baffle,to analyze the influences of horizontal wave pressure effected by the dimensionless factors,which are the relative water depth of the baffles and the wave length-height ratio.On the basis of the research results above,more practical breakwater wave pressure formula are presented,which may serve as reference for the research and design of the penetrated breakwater.