Combining with the engineering design modification project of the submerged section of a breakwater in a port area of Tianjin Port，we use the wave section physical model test method to study the structural stability of the double-layer twisted Wang block surface protection，optimize the cross-section，and propose some suggestions to improve the stability of structure. The results show that for the breakwater body，the stable mass of the upper single block is calculated by the recommended formula in Article 4.3.7 of Code of Design for Breakwaters and Revetments and the stability coefficient KD value of the twisted Wang block placed in a single layer，the calculation results can meet the requirements of structural stability. For the top part of the breakwater，when the elevation of the top of the breakwater does not exceed 0.2 times the design wave height above the design high water level，the mass of a single upper block must reach twice the mass of the upper protective surface block of the outer slope to meet the structural stability requirements. The blocks are placed regularly to keep close and connected，which can strengthen the wave-proof ability of the structure and improve the stability of the structure.