Abstract: A second-order tensor , called the anisotropy hardening tensor, is used instead of the ‘back stress’ to describe the anisotropy hardening of metal materials. Based on this tensor, a unified visco-plastic constitutive model with concise form is established. By introducing the temperature factor into this model, it is capable of predicting the visco-plastic behavior of metal materials under different loading rates and temperatures. The modeling to the thermal-mechanical behaviors of SnAgCu alloy is finished, and the numerical calculations are compared with experimental data. The results show that the prediction to the thermal-mechanical behavior of metal materials given by this new model agrees well with some experimental results.