Abstract: Based on the field data of the Xiangshan Harbor in April and July in 2010, the distribution characteristics and spatio-temporal variations of N、P、Si nutrients and the structure characteristics of them in Xiangshan Harbor were analyzed. Furthermore, the value of Si:N:P, eutrophication index (E),organic index (A) and potential eutrophication were employed to assess the eutrophication degree of the whole sea water. The results of comprehensive analysis have shown that the distribution of DIN in July and PO₄-P in April and July decreased gradually from the inner bay to the bay mouth. However, the content of inorganic nitrogen in April and silicate was relatively high in Xangshan Bay top. According to the nutrition structure, the inorganic phosphorus was the limit factor for growth of phytoplankton, and compared with Redfield ration and limit standard of chemical measure for the nutrient salts, it is accorded with the limit condition of inorganic phosphorus. According to eutrophication index (E) and organic index (A), the whole waters in Xiangshan Bay was in the serious pollution condition. Furthermore, the level of organic pollution and eutrophication was highest in Xiangshan Bay, which has a decreasing trend from Xiangshan Bay top to exit. Because of Xiangshan Bay hydrodynamic situation feebleness, the red disaster would be happened at any moment in case of hydrometeorological conditions were suitable.