Abstract: Based on Ziegler's kinematic hardening model, a new hyperboloidal constitutive model which is suitable for the plastic analysis of steel structures is presented. The model is not only capable of considering the effect of loading history, but also applicable to unsymmetric plastic cycle of strain. Thus, it can be used to perform plastic analysis of steel structures under complex dynamic load. Using this model, the response of steel structures under severe earthquake action can be traced efficiently. Numerical examples demonstrate that the model has enough precision and reliability and it can be implemented easily in computer analysis.