Abstract: In recent years,the photovoltaic on water as the core of the“fishery light complementary”has been promoted rapidly,but the impact of project construction and operation on the local ecological environment hasn’t been clear. In order to study the impact of photovoltaic power station on water ecosystem,investigations of water quality and microorganisms were conducted on 20 August 2020 at Yangzhong Tongwei fishery and photovoltaic complementary power station. The effects of surface photovoltaic on temperature,pH,dissolved oxygen,turbidity,aerosols,chemical oxygen demand（COD）,biochemical oxygen demand（BOD）and microorganisms were studied and evaluated by category analysis. The results suggest that during the operation of Yangzhong Tongwei fishery and photovoltaic complementary power station,the water temperature was reduced by about 0.5 ℃,the pH was lower than the natural site for most of the time,the dissolved oxygen had double peak,the turbidity was decreased by 11.83 NTU,the average concentration of chlorophyll a was decreased by 10.1 mg/L,the COD and BOD as pollution indicators did not increase abnormally,and the structure and abundance of the microbial population remained basically unchanged. Photovoltaic power station on water inhibits algae photosynthesis,which plays a positive role in maintaining the stability of water environment in summer and reducing the occurrence of water bloom. The results of this paper provide a scientific basis for constructing the regional ecological environment effect assessment system and the ecological restoration and protection measures under the influence of water photovoltaic project.