Abstract: Based on the principle of critical plane approach,a multiaxial fatigue damage model is proposed in this paper,which can be applied to axial-torsional loading.Three parameters on the critical plane are considered in this model,which takes into account not only the maximum shear strain range and normal strain range on the critical plane,but also the effects of the additional cyclic hardening caused by the non-proportional loading and the mean stress on the fatigue life.Additionally,its accuracy for life evaluation is relatively high,and it is convenient for engineering application because of no material constants.The capability of fatigue life prediction for the proposed fatigue damage model is verified by the experimental data from constant amplitude axial-torsional loading of Inconel 718 steel,GH4169 alloy,and Haynes 188 superalloy.Prediction results agree well with the experimental results.