Abstract: Based on a largest deep-water open caisson, the centrifuge model tests simulate the seepage field caused by mud suction during sinking when the caisson is buried more than 35 m deep. By comparing and analyzing the forces with the measured data from the prototype caisson, the main characteristics are as follows: the distribution of the lateral pressure is small at the step, the stress relaxes near the blade foot, and it concentrates in the upper and lower sections of the step, while it is more obvious below the step. When the lateral resistance during sinking is greater than the heightening, according to the distribution characteristics of lateral pressure, the method for calculating the side resistance in the vertical state of the caisson is given. The analysis also shows that the seepage effect caused by the mud suction will make the soil at the lower section of side wall become loose, and the lateral pressure is greatly reduced and negatively correlated with the seepage force. And may break the stress balance of the caisson and cause gushing sand and sudden sinking. When sinking, the extrusion of side wall will cause stress concentration and the increase of the excess pore water pressure. After sinking, the excess pore water pressure will dissipate rapidly along the drainage path, and vertical consolidation of soil on the sidewall occurs, and part of the stress concentration of soil caused by subsidence will slowly dissipate.