This paper describes a simple procedure for evaluating deformation behavior of clay foundation under embankment, using a soil-water coupled finite element method based on finite deformation with an elasto-plastic model. The simplified method for determining the soil parameters and ground modeling is estimated using liquid limit, plasticity index and natural water contents only. Reasonable agreements have been obtained between measured and computed values for vertical deformation and excess pore pressure of the well documented case history of the Kanda trial embankment built on a deep soft ground. Lateral displacement, however, is notoriously difficult to predict even approximately, to overcome this, we also investigate the effects of Poisson's ratio on the deformation analysis. The analytical results obtained by the present methods are found to be reasonable, considering the idealized assumptions made.