Diffusion　Reflectance　Spectroscopy　(DRS)　was　employed　to　study　the　surface　phase　structure　of　ZrO2-based　catalysts.　The　effect　of　calcining　temperature,　and　the　addition　of　Al2O3　and　platinum　on　the　surface　and　bulk　phase　structures　of　zirconia　was　studied　by　DRS　combined　with　XRD,　DTA　and　XPS.　The　same　trend　was　observed　that　heating　to　higher　temperatures　results　in　the　conversion　to　monoclinic　zirconia　in　undoped　samples,　while　incorporation　of　an　appropriate　amount　of　Al2O3　would　stabilize　the　tetragonal　phase　zirconia.　And　the　reduction　processing　of　Pt/ZrO2　affects　crystallization　and　phase　transitions,　resulting　in　certain　fraction　of　tetragonal　ZrO2　transferred　to　monoclinic　ZrO2.　The　DRS　shows　an　appreciable　difference　in　the　corresponding　XRD　spectra　that　more　monoclinic　zirconia　formed　on　the　surface　of　catalyst　during　the　reduction　processing　of　Pt/ZrO2,　compared　to　the　bulk　of　catalyst.