Abstract: According to the survey data of marine ecological environment of Dongshan Bay in 2011, the author analyzed the temporal-spatial distribution characteristics and influencing factors of Hg and As.The results showed that in May, the concentration of Hg was same on the surface and bottom of water, as was higher at the bottom than on the surface. In August, the contents of Hg and As on the surface were almost the same as at the bottom.The contents of Hg and As in summer were higher than in spring.In May, the contents of Hg and As were high near the Bachimen Dock and the culture areas, which decreased gradually from the central of Bay to the bay head and outer. In August, the concentrations of Hg and As were well distributed because of the water exchanging. The concentrations of Hg and As had positively correlation with temperature, but negatively correlation with pH and DO. The contents of Hg and As of seawater met the second degree of Sea Water Quality Standard,which showed that seawater of Dongshan bay was lightly contaminated by Hg and As and had good seawater quality.