Abstract: Soft clay was magnificently nonlinear,hysteretic and accumulatively deformable under dynamic load,and therefore it was more reasonable to describe its stress-strain relation with elasto-plastic models.Based on the mixed hardening plastic modulus field theory,an incremental elasto-plastic dynamic constitutive model for the saturated clay under the undrained condition,expressed in the form of total stress,was developed.Its yield surface continuously varied.The model overcame the defect that there was conjugate point thus singularity in plastic modulus field in the nested yield surface model.In addition,the model didn’t need to remember the stress inverse surface and to judge whether the current yield surface exceeded the stress inverse surface.Owing to that the existing elasto-plastic dynamic model was unable to consider the effect of anisotropic consolidation on soil deformation and failure,so it was attempted in this paper to reflect this effect by introducing an anisotropic deviatoric tensor of stress in the failure surface equation.The predicted stress-strain relation of soil was compared with the test and the calculated results of existing model.It is shown that the proposed model could depict the primary soil dynamic characteristics and the effect of anisotropic consolidation on soil deformation and failure.