A　novel　route　for　rapid　synthesis　of　ultrafine　WC-Co　cemented　carbides　with　homogeneous　binder　phase　distribution　is　reported.　The　composite　powder　is　produced　by　in　situ　reduction-carbonization　reactions　by　using　WO2.9,　Co3O4　and　carbon　black　as　raw　powders.　The　reaction　equilibrium　and　phase　stability　are　studied　by　thermodynamic　calculations.　The　WC-Co　composite　powder　is　condensed　by　spark　plasma　sintering　(SPS)　to　obtain　the　cemented　carbides　bulk.　The　sintering　temperature　is　lower　than　that　in　the　conventional　sintering　methods　by　150C,　while　the　sintering　time　is　remarkably　reduced　by　3-5　times.　The　high　performances　of　the　hardness　and　the　fracture　toughness　are　obtained.　The　experimental　results　confirm　that　the　present　processing　scheme　of　in　situ　reduction-carbonization　reactions　and　subsequent　SPS　sintering　is　an　efficient　way　to　prepare　WC-Co　cemented　carbides,　and　is　apparently　superior　to　the　conventional　long-period　techniques　of　preparing　composite　powder　and　cemented　carbides　bulk.