Abstract: The shear stress gradient effect is studied in this paper. First, based on the stress field intensity approach, which is very commonly used for the fatigue life prediction of notched specimens, a novel shear stress parameter is proposed. In this parameter, a weighted average stress is calculated near the fatigue critical point according to the relative shear stress gradient. Then, a series of tension-compressional and torsional fatigue tests are conducted on 30CrMnSiA steel. Based on the test results, the existence of the shear stress gradient effect is verified. It is found that, compared with the tension-compressional loadings which have no stress gradient, the specimens have longer fatigue lives under torsional loadings at the same stress level. The proposed shear stress parameter is proved to have a good capability to describe the shear stress gradient effect.