Spray　granulation　was　carried　out　using　the　ultrafine　WC-Co　composite　powders　with　an　average　particle　size　of　300　nm　as　the　raw　material　which　was　rapidly　synthesized　by　the　technique　of　in　situ　reactions.　The　standard　funnel　method　and　scanning　electron　microscope　(SEM)　were　employed　to　measure　the　apparent　density　and　characterize　the　morphologies　and　structures　of　the　granulated　powders,　respectively.　Moreover,　the　influences　of　the　slurry　composition,　the　drying　temperature　and　the　particle　size　of　raw　powders　on　the　apparent　density　of　the　granulated　powders　were　studied　by　combining　the　experimental　and　theoretical　calculation　results.　The　results　indicate　that　the　apparent　density　of　the　granulated　powders　reaches　2.31　g/cm3　as　the　solid　content　of　the　slurry　increases　up　to　70%　(mass　fraction).　But　with　the　increase　of　the　organic　binder　content,　the　apparent　density　of　the　granulated　powders　firstly　increases,　and　then　drops　down.　The　optimum　binder　content　and　dispersant　content　is　2.5%　(mass　fraction)　and　1%-2%　(mass　fraction),　respectively.　The　spray　drying　temperature　greatly　influences　the　morphology　and　the　apparent　density　of　the　granulated　powders　and　the　optimum　value　is　150°C.　The　highest　density　of　granulated　powders　essentially　depends　on　the　particle　size　of　the　raw　powders.