WO3,　Co　and　carbon-mixed　powder　was　in-situ　synthesized　to　compact　WC-Co　bulk　by　spark　plasma　sintering.　The　effect　of　the　synthesis　parameters　and　the　carbon　content　on　the　phase　as　well　as　the　density　and　the　microstructure　of　the　bulk　have　been　studied.　The　hardness　and　the　KIC　of　the　bulk　have　been　determined.　When　the　carbon　content　is　low,　Co3W3C　or　Co3W9C4　appear　and　the　density　is　high.　Only　WC　and　Co　are　found　with　higher　carbon　content.　Free　carbon　appears　with　the　high　carbon　content,　and　the　density　is　low.　The　grain　size　of　WC-Co　bulk　is　below　0.5　μm　with　inhibitor　VC,　Cr3C2.