Abstract: Uniaxial (tension-compression and torsion paths) and nonproportional multiaxial (circular, rhombic and butterfly paths) loading fatigue tests were carried out on HRB335 steel. On the basis of the tests, the parameters of equivalent strain method, KBM critical plane model and critical plane model with stretching factor (stretching factor model) were calibrated, and the effectiveness of each model for multiaxial fatigue life prediction of HRB335 steel was compared and analyzed. The stretching factor was improved by introducing path nonproportionality and a material additional strengthening parameter, and the prediction of the improved stretching factor model was verified. The results show that the fatigue life prediction of HRB335 steel by the equivalent strain method was mostly out of the triple error range. The fatigue life prediction by the KBM critical plane model and stretching factor model under circular and butterfly path loading partly exceeded the triple error range. The fatigue life prediction of HRB335 steel under five loading paths by the improved stretching factor model was all in the triple error range, and the multiaxial fatigue life prediction of Q235 steel and 304 stainless steel was also consistent with the test results, indicating the model was reasonable and effective.