Abstract: Titanium nitride (TiN) thin films were prepared on Si(100) substrates by DC reactive magnetron sputtering method.XRD and AFM were employed to characterize the structure and morphology of the TiN thin films.The square resistances were measured using four-probe meter.The optical reflectances were measured by ultraviolet and visible spectrophotometer.The influence of Ar and N2 flow ratio on the structure and properties of TiN thin films was investigated.The results show that the main component of the thin films was cubic TiN with (200) preferred orientation at different Ar and N2 flow ratios.When the Ar and N2 flow ratio increased the thickness of the thin films increased gradually,while the surface roughness and resistivity decreased firstly then increased.The surface roughness and resistivity reached a minimum value when the Ar and N2 gas flow ratio was 15∶1.The reflectance of TiN thin films had little relation to the flow ratio of Ar and N2.