The　evolution　of　the　sintering　neck　sizes　was　observed　in　experiments　on　the　conductive　powder　particles,　based　on　which　a　model　that　describes　the　distributions　of　the　current　density　and　the　temperature　increase　in　the　spark　plasma　sintering　(SPS)　process　was　developed.　The　simulations　show　that　the　sintering　neck　with　smaller　size　grows　prior　to　the　neck　with　larger　size.　The　reason　is　that　the　current　density　at　the　smaller　necks　is　higher　than　that　at　the　larger　necks,　hence　there　is　a　higher　temperature　increase　at　the　same　sintering　stage.　As　a　consequence,　the　neck　size　distribution　becomes　homogeneous　with　the　densification　process.　A　unique　‘self-adjusting’　mechanism　for　the　neck　growth　was　proposed　for　the　SPS　process,　which　explains　the　advantageous　features　of　SPS　densification.　©　2008　Inderscience　Enterprises　Ltd.