The shear resistance of the bottom plate of a caisson often controlls the thickness of the bottom plate，and there is limited research on the distribution law of shear force.To address this issue，finite element method is used to calculate different combinations of working conditions.The maximum shear force distribution at the edges of plates with four-side fixed under uniform load，and the relationship between the maximum shear force and the thickness，length and aspect ratio of the plate are studied.The general rule of the ratio of maximum shear force to average shear force is obtained.The results show that the distribution of shear force at the edge of the plate follows a parabolic shape.The maximum shear force at the edge of the plate is less than the maximum shear force calculated by the elastic thin plate theory.Under the same scale and load conditions，the maximum shear force at the edge of the plate will decrease as the thickness of the rectangular plate increases.As the size of the rectangular plate increases，the maximum shear force at the edge of the plate will rapidly increase，and the ratio of the maximum shear force to the average shear force will also increase.For commonly used caissons longitudinal and transverse partition wall spacing and bottom plate thickness，the ratio of the maximum shear force at the edge of the plate to the average shear force is usually 1.3 to 1.6.This paper summarizes the relationship between shear force distribution and grid scale,aiming to provide reference for similar engineering designs.