Floating breakwaters are widely used in coastal engineering due to their effective wave attenuation capabilities.To address the long-period and large-amplitude wave environment faced by offshore photovoltaic(PV)farms,this study optimizes floating-box breakwaters by attaching inclined wing plates to the bottom of the floating boxes and adopting a double-floating-box configuration.Based on the time-domain wave height response signals under irregular wave conditions obtained from scaled model tests,the wave transmission coefficients are calculated to compare and analyze the wave attenuation performance of floating breakwaters with different structural forms,and the mooring chain forces as well as the motion states of the floating boxes are further measured.The results show that both measures can reduce the wave transmission coefficient and improve the wave attenuation performance of the structure.For every 0.5 m increase in the water entry length of the inclined wing plate,the transmission coefficient decreases by approximately 15%.Selecting the local optimal solution from the experiments,a double-floating-box floating breakwater with inclined wing plates attached to its bottom is designed.This structure exhibits smaller mooring chain forces and has an obvious restraining effect on the surge,heave,and pitch motions of the floating boxes,which is an effective approach in engineering design.