A composite layer was prepared on the surface of Ti-6Al-4V alloy by nitriding-sulfurizing composite treatment,and its microstructure and phase structure were examined by scanning electron microscopy(SEM)and X-ray diffraction(XRD),respectively.The tribological performance was measured to investigate its dependence on the nitriding-sulfurizing composite treatment process.The results indicated that the composite layer was mainly comprised of Ti2N,TiN,and TiS2.It was found that the composite layer exhibited superior tribological properties under dry friction and absolute sliding conditions due to the formation of sulfides with self-lubricating function.