The　in-situ　reduction　and　carbonization　reactions　were　used　to　synthesize　the　WC-Co　composite　powder　with　nanoscale　particle　sizes.　The　nanocrystalline　WC-Co　cemented　carbides　bulk　material　was　prepared　by　spark　plasma　sintering　(SPS).　Results　show　that　the　particle　size　of　the　grain　growth　inhibitor　VC　has　a　significant　effect　on　the　microstructure,　grain　size　and　properties　of　the　prepared　nanocrystalline　WC-Co　bulk　material.　When　the　VC　particle　size　is　below　100　nm,　the　prepared　nanocrystalline　WC-Co　bulk　has　a　mean　grain　size　of　about　70　nm.　It　has　a　high　density,　pure　phase　constitution,　homogeneous　grain　size　distribution　and　excellent　mechanical　properties,　with　a　Vickers　hardness　of　19.84　GPa　and　a　fracture　toughness　of　12.10　MPa.m(1/2).