Abstract: The evolution of strains at the root of U-shaped （with notch radius of 0.2 and 1.0 mm） and V-shaped （with notch angle of 45° and 90°） notches during fatigue under different loading levels were obtained by digital image correlation technique. The effects of the load amplitude （0.5, 0.7, 1.0 kN） and the load ratio （0, 0.3, 0.5） on the ratcheting strain and strain amplitude at the notch root were investigated. On the basis of the evolution of the steady state ratcheting strain rate at the notch root and stress concentration fraction, two fatigue life prediction models were established considering the nominal stress amplitude and the load ratio effects, respectively. The results show that with the increase of load amplitude, the ratcheting strain and strain amplitude at the root of notches increased. With the increase of load ratio, the ratcheting strain at the root of notches increased, while the strain amplitude changed little. The predicted values of the fatigue life by the prediction model considering the nominal stress amplitude and load ratio were mostly within a 1.5-fold error band, with the maximum not exceeding a 1.75-fold error band. The model was accurate. The fatigue life prediction error by the model considering the influence of load ratio was higher than that considering load amplitude influencing. The model's fatigue life prediction error for U-shaped notch sample was higher than that for V-shaped notch sample.