Abstract: With the rapid development of new energy vehicles, the reliability and durability of rotating shafts in their transmission systems were crucial to the overall performance and operational safety of vehicles.Fracture occurred in a rotating shaft of a new energy vehicle. Methods including macroscopic observation, chemical composition analysis, scanning electron microscopy analysis, metallographic examination, hardness test and penetrant test were adopted to reveal the influence mechanisms of grinding cracks, insufficient depth of carburized and quenched layer, and non-metallic inclusions on the fracture of the rotating shaft.The results show that grinding cracks and grinding burns were the main causes of early rotating-bending fatigue fracture of the rotating shaft, while insufficient depth of carburized and quenched layer and non-metallic inclusions further accelerated the initiation and propagation of cracks.