The　kinetics　of　Mg2Sn　synthesis　reaction　was　studied　under　isothermal　condition　in　the　present　paper.　Results　indicated　that　the　isothermal　reaction　of　Mg2Sn　was　controlled　by　two　reactive　mechanisms:　the　nucleation　and　growth　control　in　the　first　stage　corresponding　to　the　Avrami　exponent,　m　approximate　to　3,　and　the　phase　boundary　control　in　the　second　stage　corresponding　to　m　approximate　to　1.1.　The　reactive　activation　energy　(E-a)　for　the　two　stages　was　293.6　kJ.mol(-1)　and　358.1　kJ.mol(-1),　respectively.　The　microstructural　evolution　in　Mg2Sn　synthesis　process　was　in　good　agreement　with　the　two　reactive　mechanisms.