Abstract: Based on the divisional investigation of seawater quality from 2007 to 2015 in Xiangshan bay, the spatial distribution and the interannual variability of the main pollution factors (including DIN, DIP, oil, and heavy mental Pb) were analyzed. Eutrophication Index (E) and Potential Ecological Risk Index(RI)are used to evaluate the interannual eutrophication condition and the ecological risk of heavy metals in surface sediments. The result shows that the average concentration of DIN, DIP and the oil which are the main pollution factors of the seawater quality in Xiangshan bay decreased from the entrance to the bottom. Although relatively low values of eutrophication index occurred in some years, the problem of eutrophication is still serious. Analysis of the potential ecological risk of heavy metals in surface sediments from the middle part of Xiangshan bay show a slight increase trend from 2006 to 2013. As for land-based pollution, Principal Component Analysis (PCA) was used to distinguish that nitrogen fertilizer and livestock are the main sources of the nitrogen pollution, while the phosphorus pollution is mainly resulted from livestock and phosphorus fertilizer. In addition, mariculture is the another significant source of the eutrophication.