Abstract: Thin films of MT-Ti(C, N) with different nitrogen and carbon contents were prepared on cemented carbide substrates using the chemical vapour deposition. It was found that carbon source had decisive effect on the ratios of C/N, and that the microstructure of MT-Ti(C, N) varied as the ratios of C/N changed, which was analyzed by SEM, TEM and EDS. The results showed that C₂H₄ gas could help to increase the ratio of C/N compared to mono CH₃CN, and that as the ratios of C/N increased, the grain size of MT-Ti(C, N) decreased. It was also shown that the ratios of C/N played an important role in the corresponding scratch resistance and nanohardness.