Objective:　To　investigate　the　biocompatibility　of　diamond-like　carbon　(DLC)　coated　nickel-titanium　shape　memory　alloy　(NiTi　SMA)　in　vitro　and　in　vivo.　Methods:　The　in　vitro　study　was　carried　out　by　co-culturing　the　DLC　coated　and　uncoated　NiTi　SMA　with　bone　marrow　mesenchymal　stem　cells　(MSCs),　respectively,　and　the　in　vivo　study　was　carried　out　by　fixing　the　rabbits＇　femoral　fracture　model　by　DLC　coated　and　uncoated　NiTi　SMA　embracing　fixator　for　4　weeks,　respectively.　The　concentration　of　the　cells,　alkaline　phosphatase　(AKP),　and　nickel　ion　in　culture　media　were　detected,　respectively,　at　the　first　to　fifth　day　after　co-culturing.　The　inorganic　substance,　osteocalcin,　alkaline　phosphatase　(ALP),　and　tumor　necrosis　factor　(TNF)　in　callus　surrounding　fracture　and　the　Ni(+)　in　muscles　surrounding　fracture　site,　liver　and　brain　were　detected　4　weeks　postoperatively.　Results:　The　in　vitro　study　showed　that　the　proliferation　of　MSCs　and　the　expression　of　AKP　in　the　DLC-coated　group　were　higher　than　the　uncoated　group　(P　＜　0.05),　while　the　uncoated　group　released　more　Ni(2+)　into　the　culture　media　than　that　in　the　coated　group　(P　＜　0.05).　The　in　vivo　study　revealed　that　the　inorganic　substance　and　AKP,　osteocalcin,　and　TNF　expression　were　significantly　higher　in　the　DLC　coated　NiTi　SMA　embracing　fixator　than　that　in　the　uncoated　group　(P　＜　0.05).　Ni(2+)　in　liver,　brain,　and　muscles　surrounding　the　fracture　were　significantly　lower　in　the　DLC　coated　groups　than　that　in　the　uncoated　group　(P　＜　0.05).　Conclusion:　Nickel-titanium　shape　memory　alloy　coated　by　diamond-like　carbon　appears　to　have　better　biocompatibility　in　vitro　and　in　vivo　compared　to　the　uncoated　one.