The elastic-plastic constitutive function of 30CrMnSiA steel is presented based on the total theory of plasticity, and the low cycle fatigue life of 30CrMnSiA notched specimens is predicted by damage mechanics-finite element method. The results are compared with the corresponding experimental results. The results show that the elastic-plastic constitutive relation method based on the total elastic-plastic theory is reasonable, and the fatigue life prediction results basically meet the engineering requirements. The low cycle fatigue life prediction of 30CrMnSiA notched specimens can be carried out based on the damage mechanics method.