Abstract: Soft clay is influenced by the time-dependence of viscosity and consolidation as well as coupling effect of moisture. In order to study the effect of moisture content on soft clay foundation, by introducing the elastic-viscoplastic mechanics effects into porous media, the model for solid-liquid two-phase porous media and the governing equations for soft clay foundation are deduced, and the finite element model and program are established based on the theory of porous media, the penalty function parameter method and the Galerkin weighted residual method. Compared with the theoretical results and the observed data, it is indicated that the proposed model and procedure are suitable for simulating the mechanical behaviors of soft clay foundation.