Abstract: This paper studied the 1~3 m thick sedimentary environment in the Laizhou Bay based on the grain size information of 20 core samples. Sand and silty sand are the main components of the sediments in Laizhou Bay, and their sorting degree is poor on the whole, indicating significant influence on the formation of the sediments exerted by surrounding factors. The grain size characteristics of the sediments in Laizhou Bay obviously reflect the environment. The distribution of grain size in cores indicate different stages of forces acting on the sediments in different sea areas. In general, from the coast of Laizhou Bay to the plain under middle shallow sea, the slope of the probability accumulation curve increases gradually and the periodic differentiation becomes more and more distinct. The environmentally sensitive component of Laizhou Bay sediment is 3≤φ≤4, and coastal river properties and sediment transport path have significant effects on grain size and components. Combined with the previous research on sedimentation rate, the periodic changes of grain size and components in the eastern area of Laizhou Bay is temporally corresponding to the diversion of the Yellow River in 1855. The sedimentary environment in the middle sea area of Laizhou Bay has strong hydrodynamics and diverse material sources. The grain size of sediments in Qimudao-Diaolongzui sea area is slightly coarse, requiring a higher critical starting speed and a relatively small probability of resuspension. The Yellow River submerged delta is relatively turbulent with unstable energy. It is in the late stage of gravity flow, with energy attenuation and conversion to traction and drainage. The underwater bank slope in the southern Bay has a certain amount of sedimentation under the action of waves and tidal currents.