The　mechanism　of　neck　formation　of　conductive　pure　materials　during　SPS　was　studied.　By　using　the　pure　copper　powders　as　the　sintering　material,　the　microstructure　characteristics　of　different　sintering　stages　were　studied　and　discussed.　A　two-particle　model　was　developed　to　describe　the　temperature　distribution　from　the　center　to　the　contact　area　of　two　particles.　It　is　concluded　from　the　present　model　that,　there　is　a　greatly　inhomogeneous　distribution　of　the　temperature　in　the　particle,　the　temperature　is　higher　than　the　melting　point　even　boiling　point　of　the　material　in　neck　zone.　Consequently,　the　essence　of　the　neck　formation　is　the　melting　and　even　vaporizing　of　the　contacting　area　between　particles　due　to　the　local　extra　high　temperature.