Abstract: Seawater quality of the mariculture zones in Yanpu Bay was monitored and analyzed from 2013 to 2015. Eutrophication index and organic pollution index were used to evaluate the nutrition state and organic matter pollution of the water in this area. The results indicated that the indices, including DO and COD, satisfied the second class of seawater quality standards, whereas the concentrations of inorganic nitrogen, active phosphate and petroleum exceeded the second class of the standard. The water quality exceeded the standard much severely in winter and spring. The main pollutants beyond the standard in winter were inorganic nitrogen and petroleum, while in spring were inorganic nitrogen and active phosphate. Generally, the organic pollution was not quit serious in this mariculture zone though the eutrophication became severe.