The　wettability　and　spreading　dynamics　of　Au-30%Si　(mole　fraction)　alloys　on　graphite　were　studied　using　a　modified　sessile　drop　method　under　vacuum　at　1373-1473　K.　The　results　show　that　the　wettability　improves　with　the　temperature　increasing.　The　alloy　is　non-wetting　with　graphite　and　final　contact　angle　as　large　as　100°　at　1373　K.　When　T≥1393　K,　the　contact　angle　accelerates　apparently　with　the　temperature　increasing,　and　finally　presents　an　excellent　wettability　with　contact　angle　decreasing　to　16°.　The　formation　of　interfacial　reaction　products　SiC　resulting　in　the　continuous　decrease　of　solid-liquid　interfacial　energy,　which　provides　the　driving　force　for　wetting　and　spreading.　A　spreading　kinetic　model　is　established,　which　explains　the　wetting　mechanism　from　the　angle　of　energy　and　predicts　the　solid-liquid　interfacial　energy　decreasing　with　time　in　exponential　relationship.　The　experimental　results　are　in　accord　with　the　theoretical　calculation　in　reaction-limited　spreading.　©　2016,　Science　Press.　All　right　reserved.