Abstract: Early fracture failure of a nickel-titanium alloy medical device product occurred during fatigue testing. The fracture causes of the product were analyzed by scanning electron microscope and energy spectrometer. The results show that the early fracture of the product was due to the mechanical polishing hollow on the surface of the multi-stranded wire of the raw material, which reduced the fatigue resistance of the material and caused the early fatigue failure of the product under the action of cyclic fatigue stress. Strictly controlling the surface quality of the raw material is an important way to improve the fatigue resistance of the nickel-titanium alloy wire products.