Based on the investigation of 2004, the paper analyzed the contents of heavy metals and transitional elements in marine sediment in the Sansha Bay. The distribution characters of transitional elements, and correlation between transitional elements and heavy metals were systematically studied, and significance of the environment and material source was also discussed. The results showed good correlation between Cr, Cu, Hg,Pb and Fe2O3 in marine sediment. Mountain ranges around the Sansha Bay contain metal ore which is enriched in a variety of elements, such as Fe2O3 ,Ni and Mn. Metal ore was eroded by rainstorm and a great volume of elements was carried into marine sediment by river runoff, resulting in higher contents of Cu and Zn, which are were higher than those of the sediments of shallow sea of China and background values of soil in Fujian province. These features indicate that the heavy metals are largely from natural source, with minor from contamination.