Abstract: The effect of repairing welding passes on the fatigue property of Q345B low-alloy steel by pulsating fatigue test. The results show that the fatigue strength of once-repairing welding decreased slightly(only for 4.6 MPa) comparing with that of non-repairing welding, and the fatigue strength of second-repairing welding basically match to that of once-repairing welding, the difference between them was only 0.7 MPa. The crackinitiation and propagation area of fatigue crack had the typical fatigue fracture characteristics, fatigue end broken area morphology was quasi-cleavage and little dimple.