The mixed wave of long-period surge and wind wave has the characteristics of long-period and large wave energy，and the design of slope breakwater structure in such environment cannot be carried out by simply referring to current codes. Based on a built project，we carry out the calculation and theoretical analysis to compare and analyze the design process and physical model test verification process of the project，and obtain the key points of structural design for sloping breakwater under long-period mixed wave in the open sea. The results show that the experience coefficient in the design should be considered such as the selection of block for outer slope protection and determination of the height of the top of the wave wall. The top of the breakwater behind the wall and the slope behind the breakwater need to be strengthened especially，and the appropriate structure type of the wave break wall should be selected as far as possible on the top of the breakwater. The calculation formula of rock protection bottom in the current code is inappropriate under the condition of shallow water.