The　paper　is　focused　on　understanding　the　densification　characteristics　of　WC-Co　composite　powders　by　the　spark　plasma　sintering　(SPS)　technique,　especially　the　essential　mechanisms　for　the　distinct　differences　of　the　effects　of　WC　particle　size　on　the　densification　behavior　between　the　SPS　and　the　conventional　sintering　technologies.　For　the　particular　combination　and　contacting　state　between　WC　and　Co　after　ball　milling　in　which　Co　forms　thin　films　coating　the　WC　particles,　a　model　that　quantitatively　describes　the　densification　process　of　SPS　WC-Co　powders　with　different　WC　particle　sizes　has　been　developed.　The　calculated　results　show　that　both　the　actual　temperature　in　the　Co　film　and　the　melting　temperature　of　the　Co　film　increase　with　the　increase　of　the　WC　particle　size.　As　a　result,　the　formation　and　growth　of　the　sintering　necks　due　to　the　rapid　melting　and　solidification　of　the　Co　films　turn　to　be　weakly　influenced　by　the　WC　particle　size,　and　hence　the　SPS　densification　is　almost　independent　of　the　WC　particle　size.　The　model　calculations　are　consistent　with　the　experimental　findings　that　in　the　SPS　processes　the　temperatures　corresponding　to　the　start　of　the　densification　and　the　peak　of　the　displacement　rate,　respectively,　are　nearly　the　same　for　the　WC-Co　powders　with　different　WC　particle　sizes.