Controlling　the　conditions　of　the　oxygen　partial　pressure　and　temperature　to　prepare　the　WO2.72　(W18O49)　via　reduction　was　possible　through　thermodynamic　consideration.　WO2.72　was　synthesized　via　heating　to　1073K　in　5%　H-2-95%　Ar　mixture　gas　flow　from　ammonium　tungstate　which　was　prepared　by　hydrothermal　process.　With　the　reducing　prolonging　time,　the　products　were　changed　from　WO2.72　to　WO2　and　then　metal　W.　Thermogravimetric　(TG)　analysis　showed　ammonium　tungstate　decomposed　completely　to　WO3　at　773K.　Isothermal　reductions　using　TG　analysis　were　carried　out　at　905K,　925K,　945K　and　973K　in　5%　H-2-95%　Ar　mixture　gas　flow,　respectively.　The　whole　reduction　from　WO3　to　WO2.72　divided　into　three　parts:　initial　nucleation　and　growth　stage,　final　interfacial　reaction　stage　and　intermediate　stage,　was　controlled　jointly　by　both　mechanisms.　Fitting　results　showed　that　theinitial　stage　obey　the　one-dimensional　Avrami-Erofeev　equation,　the　apparent　activation　energy　was　132.7　+/-　1.1kJmol(-1)　and　the　pre-exponent　factor　was　4.82x10(5)min(-1);　the　final　stage　expressed　by　2-dimensional　interfacial　reaction,　the　apparent　activation　energy　was　144.0　+/-　2.1kJmol(-1)　and　the　pre-exponent　factor　was　3.20x10(5)min(-1).