Abstract: 44 surface sediment samples were collected from the Jiaozhou Bay of Shandong Peninsula for study of grain size distribution patterns and sediment types. Upon the basis, modern sedimentary environment is classified with grain size parameters and their relation with geographic locations using the method of system cluster. The result indicates that sediment samples of the study area are characterized by sandy silt, silt, silty sand, clayey silt and mud. The mean grain size varies from 1.1Φ to 7.1Φ, with an average of 5.7Φ. The silt dominates the deposits, which reaches 58.6% in average, and the average contents of sand and clay are only 23.6% and 17.3% respectively. The research area is divided into 4 different depositional zones.Ⅰ)the zone of bay top and shallow water area near the east coast.Ⅱ)the region of Daguhe River and Yanghe River underwater delta.Ⅲ)the southwest and central regions of the bay.Ⅳ)the periphery of Cangkou sand ridge and the bay mouth.