UV-Raman spectroscopy was used to study the molecular structures of TiO2 or ZrO2-supported vanadium oxide catalysts. The real time reaction status of soot combustion over these catalysts was detected by in-situ UV-Raman spectroscopy. The results indicate that TiO2 undergoes a crystalline phase transformation from anatase to rutile phase with the increasing of reaction temperature. However, no obvious phase transformation process is observed for ZrO2 support. The structures of supported vanadium oxides also depend on the V loading. The vanadium oxide species supported on TiO2 or ZrO2 attain monolayer saturation when V loading is equal to 4 (4 is the number of V atoms per 100 support metal ions). Interestingly, this loading ratio (V4/TiO2 and V4/ZrO2) gave the best catalytic activities for soot combustion reaction on both supports (TiO2 and ZrO2). The formation of surface oxygen complexes (SOC) is verified by in-situ UV Raman spectroscopy and the SOC mainly exist as carboxyl groups during soot combustion. The presence of NO in the reaction gas stream can promote the production of SOC.