Abstract: Based on 13 surface sediment samples collected from the offshore waters of Rizhao, the grain size and distribution characteristics of heavy metals were analyzed. The pollution indexes and potential ecological risk indexes were used to assess the pollution level and potential harmful effects of heavy metals to explore the origin of heavy metals and controlling factors. Results show that surface sediments can be grouped into 3 types, i.e. silt, sandy silt and silty sand. And they distribute roughly along the coastline with zonation of silty sand, sandy silt and silt in consequence toward the sea. The averaged contents of Cr, Zn, Pb, As, Cu, Cd and Hg in the sediments from high to low are 45.5, 21.8, 16.4, 8.5, 4.8, 0.113 and 0.11 μg/g, respectively. High value area of Cr, Cu, Zn and Pb distributes mainly in the nearshore waters of Futuan Estuary and in the mid-west of study area and high value area of Cd and As in the mid-eastern of the study area. The assessment shows little pollution of Cr, Cu, Zn and As and mild pollution of Cd in the study area except for some moderately polluted sites. Hg and Pb are lightly polluted at some sites. The potential ecological risk level is in order of Cd, Hg, Cu, As, Pb, Cr and Zn. Among them, Cd and Hg are medium ecological risk. Cd is of high-risk hazard at particular sites. Cu, Cr, Zn, Hg and Pb may come from the input of terrestrial fine materials while Cd and As from iron and steel smelting, coal combustion, pesticide and fertilizer application and mariculture activities etc. The spatial distribution of heavy metals in the surface sediments of the study area is mainly controlled by provenance.