Based on cnoidal wave diffraction theory,the wave potential solutions to shallow water wave diffraction by arc-shaped bottom-mounted breakwater are derived by applying the eigenfunction expansion approach,and accordingly the horizontal wave loads on breakwater are analytically calculated.The evaluating results demonstrate that the variation of incident wave angle,nonlinear influence parameter of wave,ocean condition,and breakwater structure geometry condition may have some influence on shallow water wave effects on breakwater.Compared with small amplitude wave theory,the results of maximum dimensionless wave forces from first order cnoidal wave theory are obviously larger than those predicted by small amplitude wave theory in certain shallow water condition and reflects wave nonlinear effects.