In this study, a series of cerium dioxide catalysts with varying hydrothermal temperatures and times were synthesized using the hydrothermal method, without the use of templates. The impact of varying hydrothermal conditions on the activity of cerium dioxide catalysts was investigated through experiments to examine their oxidation characteristics in soot combustion. Among the conditions tested, the hydrothermal conditions of 140 °C and 6 h yielded the most optimal catalytic oxidation of soot, with a combustion characteristic temperature (