Abstract: The survey of surface seawater quality in Long island adjacent waters was conducted in June and November, 2016.Hydrochemistry elements including temperature, pH, salt degree, DO, COD, NH₄-N, NO₂-N, NO₃-N, PO₄-P, Cr, Cu, Zn, As, Cd, Hg, Pb and oils were surveyed.The results show that the concentration of pollutants in the surface seawater of the sea area generally decreases from the Long island to the southwestern waters, decreasing to the southeastern waters, and the concentration of inorganic nitrogen is main pollutants.The results of nutrient evaluation model and organic pollution index show that the overall nutrient level of surface seawater in this area is high, the potential eutrophication level is limited, the degree of organic pollution is small and the water quality is good.