Catalytic oxidation of diesel soot particulate on CexZr1-xO2 catalysts was investigated. Results indicated that Ce/Zr ratios had a significant influence on the catalytic activities. Compared with the ignition temperature (T) of uncatalyzed soot combustion, T of Ce0.5SZr0.5O2 with the best catalytic behavior decreased by 80 degrees C. The reactant gas compositions (O-2, H2O and NO) affected the catalytic activities too. O-TPD, TG-DTA and XPS characterization results showed that CexZr1-xO2, released lattice oxygen continuously to promote the soot combustion even no gas oxygen occurred in the reaction atmosphere. The mechanisms of spill-over and reduction/oxidation functioned synergistically for soot catalytic combustion. (c) 2006 Elsevier B.V. All rights reserved.