Abstract: Based on grain size data of 184 surface sediment samples, we studied the types of surface sediment and their distribution pattern in the offshore area of the Sang Island. Grain size parameters are presented and the major factors controlling the sediments distribution discussed in this paper. The sediment of the area can be divided into 7 types, such as sandy silt, sandy gravel, gravel, etc. The sandy silt is widely distributed in the study area and the pebbly coarse sediment is mainly distributed in the coastal area of the Sang Island. Fine grained components are widely distributed in the far offshore region. The sediments are fairly sorted with positive skewness. As the initiation velocity of surface sediment is below the maximum tidal current, the sediment in the north of the Yi Island and the waterway located to the south of the Sang Islands is controlled by the tidal current. In contrast, the sediment near the beach and north coast of the Sang Island is controlled by waves.