Abstract: A cyclic plastic model in which an additional term is conducted into the evolution of backstress in order to predict nonmassing behavior of material was employed. Based on radialreturn method and back Euler integration, new stress and backstress contributions were obtained, tangent stiffness matrix for global iteration was deduced as well. The model was implemented into the commercial finite element software ABAQUS by usersubroutine UMAT. Examples were approached for polycrystalline copper which is typical nonmassing material. The results show that the finite element simulation agrees well with the experimental data.