The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de-pended on the vanadium loading.Isolated mono-vanadate species were present on the surface of catalysts at low V loading,and poly-vanadate species existed at medium V loading,but CeVO4 crystallites were formed at high V loading(V10 and V20).The catalytic performances of these catalysts for diesel soot oxidation were investigated with temperature-programmed oxidation reaction(TPO).For soot oxidation,the poly-vanadate species were mainly active sites in ordinary CeO2-supported vanadyl catalysts,but nanometer CeO2 was mainly active components in nanometer CeO2-supported vanadium oxide catalysts.Due to the nanometer effect and the good contact between the catalyst and the soot,nanometer CeO2 exhibited a very high catalytic activity for soot combustion. The nanometer CeO2 powder was prepared by the method microwave-assisted heating hydrolysis, and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings (atomic ratios: 100V / Ce = 0.1,1,4,10, and 20) were prepared by an incipient-wetness impregnation method. Spectroscopic techniques (XRD, FT-IR, Raman and UV-Vis DRS) were utilized to characterize the structures of VOx / CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de-pended on the vanadium loading. Isolate mono-vanadate species were present on the surface of catalysts at low V loading, and poly-vanadate species existed at medium V loading, but CeVO4 crystallites were formed at high V loading (V10 and V20). catalytic reactions of these catalysts for diesel soot oxidation were investigated with temperature-programmed oxidation reaction (TPO). For soot oxidation, the poly-vanadate species were mainly active sites in ordinary CeO2-supported vanadyl catalysts, but nanometer CeO2 was mainly active components in nanometer CeO2-supported vanadium oxide catalysts. Due to the nanometer effect and the good contact between the catalyst and the soot, nanometer CeO2 exhibited a very high catalytic activity for soot combustion.