Abstract: In this paper, the mechanism of vacuum stabilization of soft clay was studied based on the establishment of the model of consolidation under the action of negative pressure. By comparison with the model of consolidation under the action of positive pressure, it can be concluded that the dewatering-displacement process of the soft clay under negative pressure is the same as that under positive pressure, and thus can also be discribed and calculated by consolidation theories.To verify this conclusion, consolidation tests under the action of negative pressure were carried out in traxial equipment.A finite element program of computers is presented to evaluate the stress, pore pressure and displacemet of subsoils when acted by vacuum, and was used in engineering practice.