WO3　and　carbon　mixed　powder　can　be　in-sit　synthesized　to　compact　WC　bulk　by　spark　plasma　sintering.　The　phase,　the　density　and　the　microstructure　of　the.　sample　synthesized　at　different　temperatures　have　been　studied.　The　mechanism　of　synthesis　was　analyzed.　With　the　rising　of　the　synthesis　temperatures,　WO3　can　be　rapidly　reduced　to　WO2.72,　WO2　and　W,　then　carbonized　to　W2C　and　WC.　Each　step　of　the　synthesis　was　overlapped.　When　the　temperature　was　lower　than　1118　degrees　C,　it　is　occur　phase　changes,　but　the　density　does　not　change　significantly.　When　the　temperature　was　higher　than　1118　degrees　C,　a　small　amount　of　the　remained　W2C　disappears,　the　sample　begins　to　sinter,　the　density　of　the　bulk　is　near　the　theoretical　density.　The　microstructure　of　the　sample　changes　with　the　synthesis　temperatures.　WO2.72　was　rod　shape,　whereas　WO3,　WO2,　W,　W2C,　WC　were　granular.　The　particle　sizes　grow　from　0.2　mu　m　to　about　0.5　mu　m.　CO2　gives　off　in　the　earlier　stage　Of　WO3　reducing,　CO　gives　off　in　the　later　stage　during　SPS　synthesis.　WO2.9　does　not　appear　during　the　reducing　reaction.