Abstract: Based on the grain size data of 207 surface sediment samples in the southwestern Laizhou Bay, the distribution pattern of surface sediments is studied. The method of cluster analysis is applied to exploring its modern sedimentary environments with the help of source and hydrodynamic analysis. Results show that the surface sediments in the study area are characterized by silty sand, silt and sandy silt, and silt is widely distributed in the sea area north to the Zimai Gou. The mean grain size gradually decreases from the shore to the central part of the Laizhou Bay, while it shows a coarse-fine-coarse trend from south to north. The modern sedimentary environment in the study area can be divided into 3 zones: the high-energy silty sand depositional zone, sandy silt transitional zone and low-energy silt depositional zone. In terms of hydrodynamic environment, it presents a trend of the weakening of wave action as tidal currents are strengthened. At the same time, the source of sediments changes from rivers and beach erosion to suspension and resuspension of the Yellow River deposits.