Based on a simple mechanical model and an appropriate definition of generalized time,a constitutive equation is obtained for coupled plasticity and creep behavior of materials.A damage evolution based on a spherical void model for mixed hardening materials is obtained by means of Gurson's model.The damage evolution law is embedded in the adopted constitutive equation,and a damage constitutive equation is obtained for coupled plasticity and creep behavior of die-casting magnesium alloy.The response of magnesium alloy subjected to cyclic loads is analyzed.The validity of the proposed model is demonstrated by the satisfactory agreement between the experimental and calculated results.