Abstract: The characteristics of grain size distribution on 202 surface sediment samples in Sanggou Bay and adjacent area was analyzed, from which the distribution patterns of gravel, sand, silt and clay were specified, the sediment types were divided, and the sedimentary environments were discussed. Results show that the sediment composition is mainly silt, and the distribution of gravel and sand content is relatively concentrated, and there are 14 types of surface sediments in Sanggou Bay and adjacent area, including 8 types with gravels and 6 types no gravels, and sandy silt and silt are most widely distributed. The distribution of sediments in Sanggou Bay and adjacent area is mainly under the control of sediment supply, landforms, tidal currents, waves, and coastal currents. The sediments near shore in the western of Sanggou Bay is coarse and near the source area with limited seaward dispersion. The sediment particles outside Sanggou Bay become finer from east to west, which is related to the westward diffusion of sediment from the source of the Yellow River carried by the coastal current along coast of the western Yellow Sea. The sediment particles of inner Sanggou Bay are fine and the hydrodynamic force is weak. The gravel-bearing sediments in the seafloor ridge area of northeast and southeast of the Sanggou Bay are local near-source clastic sediments, and the fine particles are difficult to deposit because of scouring by the ocean currents.