The multi-layer floating breakwater has the advantages of light mass，simple structure，low cost，easy to move，reusable，and not limited by water depth and geological conditions. The construction area of a dredging project in Mauritania has large swells and long period waves，which affect the dredging operation of cutter suction dredger. To solve the problem of medium and long period waves interference and reduce project budget，we use Reynolds average（RANS）equation and shear stress transport（SST）k-ω turbulence model to simulate the flow distribution based on the open source fluid mechanics platform OpenFOAM，analyze the dimensional characteristics of the multi-layer floating breakwater including plate length，plate spacing，plate thickness and the influence of different wave periods on the performance of multi-layer floating breakwater，and determine main dimensional parameters affecting wave dissipation performance of multi-layer floating breakwater. The results show that the most direct and effective way to improve the wave elimination performance of the multi-layer floating breakwater is to increase the length of board. The effect of the spacing change of board on the wave elimination performance is not completely determined，and it needs to be selected according to the actual needs.