On the basis of the discussion on mechanical behavior and the detail analysis of the change of yield surface with loading on natural marine soft clay, the effects of structural yield stress on the deformation and strength characteristics of marine soft clays, are confirmed, i.e. the behavior is similar to that of overconsolidated remolded clay when the confining pressure is lower than the structure yield stress while the behavior is similar to that of normally consolidated remolded clay when the confining pressure is larger than the structure yield stress. To much better describe the above mechanical behaviors of marine soft clay, the overconsolidated remolded model proposed by Yao et al. is introduced to establish the elastoplastic constitutive model for marine soft clays. Moreover, the tensile strength existing in marine soft clay and its evolution law are also taken into consideration. The equation of strength envelope of marine deposit soft clay is further revised in the constitutive model to reflect the strength and deformation characteristics of this marine soft clay. Finally, the comparison of stress-strain-volume strain curves between the measured and predicted results shows that the elastoplastic constitutive model can describe well the mechanical behavior of the strain-hardening/softening and dilatancy characteristics; and the deformation characteristics are dependent on the confining pressure of marine soft clay.