WC-12Co　composite　powder　was　synthesized　by　reduction　and　carburization　reactions.　With　adding　various　contents　of　combined　grain　growth　inhibitors　(GGI)　VC　and　Cr3C2　into　the　WC-12Co　composite　powder,　the　effects　of　the　GGI　addition　on　the　phase　constitution,　microstructure　and　mechanical　properties　of　the　WC-12Co　coating　prepared　by　HVOF　were　investigated　by　X-ray　diffraction　(XRD)　arid　scanning　electron　microscopy　(SEM).　The　results　show　that　with　the　content　of　GGI　increasing　in　the　composite　powder,　the　abnormal　grain　growth　disappears,　homogeneous　ultrafine　grain　structure　forms,　and　the　coefficient　of　friction　of　the　coating　declines.　When　the　total　amount　of　inhibitor　is　1.0　wt%,　the　maximum　hardness　(HV0.3)　of　WC-12Co　coating　is　13　670　MPa,　and　the　wear　rate　of　the　coating　is　the　lowest.　With　further　increasing　the　content　of　inhibitor,　the　wear　rate　of　the　coating　increases,　while　the　hardness　and　the　wear　resistance　of　the　coating　decrease.