Abstract: As the rapid development of the global offshore wind power industry, the impact of offshore wind farms (OWF) on marine ecosystems has received widespread attention. This paper selects the Bohai Zhong offshore wind farm and its adjacent waters as the research object, the field survey data before the wind farm construction (April 2019) and after its operation (May 2024) are used to compare and analyze the changes in water quality, sediment quality, as well as the community structure and diversity index of phytoplankton, zooplankton, benthic organisms, and fishery resources in the water area of the wind farm. Furthermore, the impact of OWF on marine ecological environment are evaluated comprehensively. The results show that the water quality indicators in the area of the Bohai Zhong offshore wind farm and adjacent waters showed a trend of improvement after its operation, the ratios of Average concentrations of dissolved inorganic nitrogen (DIN), plumbum (Pb) and mercury (Hg) had decreased significantly by 45.7%, 22.5% and 6.8% respectively to those before the construction of the wind farm. The concentrations of surface sediment all meet the first -class sediment quality standards indicating that the sediment was in good condition, but the content of Copper in the water and sediment had increased by 9.4% and 52.2%, respectively, which should be observed as a key indicator for long-term monitoring. After the wind farm is officially put into operation, the abundance of cell abundance of phytoplankton, the biomass of zooplankton and benthic organisms had decreased by 16.9%, 64.5% and 20.0% respectively, but the species number and diversity index of the plankton community increased, indicating that the community stability of phytoplankton was enhanced, and the community stability of zooplankton was improved; the community stability of benthic was deteriorated, the advantage of benthic organisms with smaller individual size and higher tolerance to environmental changes had obvious dominance, the number of fish species and amount of fish caught increased slightly after the operation of the wind farm. Meanwhile, the artificial reef effect generated by the foundation structure of the OWF had led to a slight increase in the dominated species of fish with tactile characteristics in the fish community, and the number of species and catch volume had slightly increased by 6.6% in the mass and 30.3% in the length after the operation of the wind farm. The research results can provide a scientific theoretical basis for the construction of the intelligent ecological supervision system to the OWF ecosystems, and offer technical support for the supervision of the whole life cycle and the entire chain ecological environment for the OWF. It is of great significance for promoting the coordinated and integrated development of offshore wind power development and marine ecological protection.