Abstract: To quantify attenuation effect of photovoltaic shading on aquatic light environment, impact of photovoltaic module shading with fixed-structure fishing-photovoltaic complementation system was investigated at Dengbu Island, Zhoushan City, Zhejiang Province．Through a field measurements and numerical simulations combination approach, spatial distribution characteristics of light environment within system were analyzed, focusing on inter-panel areas, under-panel areas, and at varying water depths．Variation patterns under sunny, cloudy, and rainy conditions were compared and assessed．Results demonstrated that photovoltaic modules shading significantly impacted aquatic light environment during treatment．Illuminance followed an exponential decay trend with increasing water depth, accurately modeled by fitted equation y=aexp(−x/b)+c．On sunny days, the maximum average illuminance over water surface between in inter-area of photovoltaic array panels reached 8.06 klx, exceeding 1.5 times that under panels．As water depth increased, the minimum average illuminance under panels sharply decreases to 0.15 klx, approaching dim light threshold．On overcast days, shading effect was further intensified．During aquaculture cycle, inter-panel area had a mean water surface light penetration rate of 48.90% due to reduced shading, significantly higher than 35.21% observed in sub-panel area．Exponential decay model precision for vertical light distribution in aquatic environments has been validated, providing scientific basis for optimizing critical engineering parameters including photovoltaic modules spacing and installation height．