The contents of heavy metals in surface sediment samples collected from the coastal areas in Jiangsu province in 2013 were measured and their ecological risk were assessed with the Hakanson's potential ecological risk index and Geo-accumulation index, respectively. Together with measurements of these samples in total organic carbon (TOC) and particle size, the characteristics and sources of the selected heavy metals were also discussed with an approach of multivariate statistical analysis. The results showed that the contents of Zn, Pb, Cd and Hg in surface sediments were less than China's national first-class benchmark (CFCB) in marine sediment quality. The 9.38% of Cu, 6.25% of Cr and 6.25% of As samples were high than CFCB, respectively, but less than the China's national second-class benchmark (CSCB). The contamination in the investigated areas was at a low level on the whole, with an order of the degree Cr> As> Pb> Hg> Cd> Cu> Zn. The potential ecological risks were also at low levels for these metals with a descending order Hg> Cd> As> Pb> Cu> Cr> Zn. Hg was the major contaminant among the metals. The contents of the selected metals were significantly positively correlated with that of TOC, but negatively correlated with particle size. Anthropogenic sewage effluent from industry and residents were the primary agents for Cu, Cr, Zn, Pb and Cd in the sediments, but agricultural source should have contributed to the most of As, and organic degradation accounted for the most of Hg.