Abstract: The outer ring of a certain type of yaw double row ball bearing in wind-power was fractured during service. The fracture reason of the bearing outer ring was analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, mechanical property test, scanning electron microscope and energy spectrum analysis. The results show that the stress concentration existed at the fracture source of the bearing outer ring, the friction plastic deformation damage existed on the contact surface, and the fatigue cracks occurred at the corrosion part and gradually expanded, finally led to the fracture of the bearing outer ring.