Nanocrystalline　diamond　films　have　been　synthesized　by　microwave　plasma　enhanced　chemical　vapour　deposition　using　H-2/CH4　as　the　reactant　gas.　Nanocrystalline　diamond　thin　films　with　surface　roughness　of　11.8　nm　were　obtained　on　silicon　substrates.　The　nanocrystallinity,　surface　roughness　and　hardness　were　characterized　by　the　Raman　spectroscopy,　X-ray　diffraction　(XRD),　atomic　force　microscopy　and　Nano　Indentation,　respectively.　The　Raman　spectra　of　the　films　exhibit　a　band　near　1145　cm(-1)　and　XRD　patterns　indicate　the　presence　of　nanocrystalline　diamond.　The　hardness　value　of　individual　test　point　is　approximately　102　GPa　and　the　average　hardness　of　thin　film　could　reach　86　GPa.