Abstract: X-ray diffraction (XRD), auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface properties of the N⁺-ion-implanted TiNi alloy. There is a high nitrogen content region at the outermost surface of the N⁺-ion-implanted TiNi alloy. The detected nitrogen exists mainly in the form of TiN. Small amounts of Ti₃O₅ and TiO₂ also exist on the surface of the N⁺-ion-implanted TiNi sample. The modified layer of the N+-ion-implanted sample can work as an obstacle layer of the nickel’s dissolution, which obstructs Ni dissolving from the TiNi surface effectively.