The bucket foundation penetrated soil is analyzed. Constitutive relationship of marine soft clay has been studied by using the principle of J2 flow theory and isotropy. The volumetric strain model which is established by combining finite element method is provided to the theoretical model of dynamic physical parameter. According to the characteristic of bucket foundation during suction penetration

combining constitutive relationship and model of dynamic physical parameter

the stress equation is established by principle of effective stress; and the flow equation is established by instantaneous law of conservation of mass. And solvability condition of aforementioned equation is derived. A new mathematic model of fluid-soild coupled flow is established to solve flow field of bucket foundation during suction penetration.