New constitutive model of swelling soil material is proposed in this study to evaluate mechanical characteristics. From the consolidationt est of the compactedb entonitem aterial, it appears that nonlinearity at the unload stage of the test is greater in comparison with ordinary clay material. These characteristics are considered that original Cam-clay model is not applicable for the compacted bentonite material. Therefore, the new parallel system which includes the swellinge lement and the elast-plastice lement to show the nonlinear behavior of the unload stage is introduced. From the result of the simulation of the triaxial compression test, it is demonstrated that the stress path and the relationship of stress-strain are approximately simulated by the new model.