Nano-diamond　was　directly　synthesized　on　Si　substrate　by　hot　filament　chemical　vapor　deposition　under　different　deposition　conditions　using　CH4　and　H2　as　the　reaction　gases,　and　it　was　characterized　by　high　resolution　scanning　electron　microscopy　and　micro-Raman　spectroscopy.　The　results　indicate　that　the　nano-diamond　particles　were　deposited　on　Si　substrate　when　the　glow　discharge　was　continually　applied　in　hot　filament　chemical　vapor　deposition　system.　However,　nano-diamond　film　was　formed　by　hot　filament　chemical　vapor　deposition　after　diamond　nucleation　by　glow　discharge.　The　formation　of　diamond　with　different　structure　results　from　the　difference　which　the　non-diamond　phase　is　etched　and　the　different　motion　of　the　precursors　which　form　diamond　under　different　deposition　conditions.