Objective To investigate the effects of hole-expansion on fatigue property of AM50 magnesium alloy. Methods AM 50 magnesium alloy was treated by hole-expansion, and beneficial compressive residual stress was introduced onto the sample surface, which was measured by X-ray diffraction technique. Meanwhile, the fatigue properties of both untreated and untreated samples were tested under sinusoidal wave load, the fatigue life and fatigue crack growth rate were analyzed, and the effects of hole-expansion on fatigue properties of AM50 magnesium alloy were studied. The fatigue fracture was analyzed by the SEM technique. Results The experimental results showed that the compressive residual stress layer reached 5. 5 mm around the hole after hole-expansion, and the maximum value was -563 MPa. Fatigue life increased from 28 936 cycles to 300 556 cycles by 9 times, while the fatigue crack growth rate greatly decreased. Conclusion SEM analysis showed that the fatigue initiation transferred inside the hole-expansion layer, which indicated that hole-expansion could obviously inhibit fatigue crack initiation and effectively enhance fatigue life.