As a thin-walled member，the thickness of the outer wall and partition wall of a caisson is usually less than the thickness of its bottom slab. Hence，it is difficult to impose effective constraints on the bottom slab，which does not conform to the assumption of the four-edge consolidation slab in the current specification. Using the finite element model to simulate the actual constraint effect of the outer wall and partition wall of a caisson on the bottom slab，we analyze the internal force distribution of the bottom slab of the caisson and compare the calculation results with those of the four-edge consolidation slab. The results reveal that the mid-span bending moment calculated by the four-edge consolidation slab is about 10% smaller. When there is no cantilever toe plate，the bending moment of the support calculated by the four-edge consolidation slab is 25% larger. When there is a cantilever toe plate，that calculated by the four-edge consolidation slab is smaller，and the deviation degree is related to the scale of the cantilever toe plate. The relevant conclusions are of guiding significance for the design of caissons.