Abstract: A total of 140 surface sediment samples were collected from the Liaodong Bay for investigation of grain size distribution pattern in this study.Grain size parameters are calculated and the sediment types classified.Results show that the surface sediments of Liaodong Bay are characterized by sandy silt (sZ), sandy mud (sM) and muddy sand (mS).The mean grain size varies from -0.06 to 7.42 Φ, with an average value of 4.92 Φ.The surface sediments of the eastern Liaodong Bay were generally coarser than those in the western part, as the sand content increases eastward.The sediments delivered by rivers around the Liaodong Bay are the major sediment source, while the dispersal of sediment is mainly controlled by the combined effects of tidal and currents systems.According to sediment types, sources and hydrodynamic conditions, the study area can be divided into five depositional areas:the mud deposits in the northern Liaodong Bay, the sandy deposits in the western Liaodong Bay, the mud deposits in the southwestern Liaodong Bay, the sandy deposits in the Liaodong shoal and the relict deposits in the central part of the Liaodong Bay.