Abstract: Submerged semi-circular breakwaters are widely used in the port engineering. The numerical wave generation method based on the theory of momentum source by using fluent simulation is adopted in the study of the changing laws and distribution of the wave pressures on the surface of submerged semi-circular breakwater. By means of the π theorem， the effects of wave steepness， water depth， and wave-length on the amplitude of wave pressures on its surface are analyzed. Besides， through the statistics， the position and occurring probability of the maximum amplitude of the wave pressure on the surface of the semi-circular breakwater are given in the study. The analysis results show that the wave steepness has a large influence on the changing trendency of the amplitude of the wave pressure at the crest and back sea side of the breakwater. The amplitude of the wave pressure at both sides of the submerged semi-circular breakwater is different with different relative depths. The maximum amplitude of the wave pressure generally occurs at the crest or nearby the back sea side. The maximum dynamic wave pressures mainly occur at two bottom-toes of the semi-circular breakwater. With the increasing of wave height， the distribution of dynamic wave pressure on the surface of the semi-circular breakwater changes from symmetric distribution to asymmetric distribution.