Wave is one of the most important hydrodynamic factors affecting coastal breakwaters.The long-period wave can penetrate the wave-permeable breakwaters,which has great impact on the hydrodynamic environment inside the breakwater,and brings some difficulties to the demolition and new construction of the breakwater and other hydraulic structures.In view of the breakwater project at the entrance of a canal in west Africa,the construction characteristics and difficulties of each item of breakwater project are analyzed according to the problems such as the long period wave influence environment and the difficulty of water construction,and the corresponding solutions are formulated,finally the reconstruction of breakwater is completed successfully.