A　differential　thermal　analyzer　(DTA)　and　a　X-ray　diffractometer　(XRD)　were　used　to　study　the　solid　transformations　in　binary　SnO2-CeO　2　oxide　system.　For　100wt%　Sn　and　100wt%Ce,　the　transformations　from　amorphous　xerogels　to　rutile　and　fluorite　start　from　about　310　and　250°C,　respectively.　The　crystallizations　to　two-phase　mixtures　of　rutile　and　fluorite　take　place　at　higher　temperatures.　The　two-phase　mixtures　appear　in　the　region　whose　composition　is　between　about　Sn-10wt%Ce　and　Sn-75wt%Ce.　Sintered　at　450°C　for　one　hour,　rutile　phase　dissolves　about　10wt%　fluorite,　and　fluorite　dissolves　about　25wt%　rutile.　Precipitation　reactions　take　place　when　the　sintering　temperature　is　raised.　The　phenomenon　that　precipitation　reactions　are　observed　for　rutile　and　fluorite　solid　solutions　means　that　lower　temperature　sintering　produces　solid　solutions　with　high　supersaturation.　In　the　as-sintered　samples,　the　grain　sizes　are　fine　nano-crystals　and　the　complicated　microstructures　help　the　other　cations　to　locate　at　discontinuous　regions.