The properties of Sn-Ce solid solution have a significant effect on the CO oxidation performance of the Pd/Sn1-xCexO2 catalyst. Herein, we compared the effects of Sn-rich and Ce-rich supports on the catalytic performance of the Pd/Sn1-xCexO2 catalysts. Our results show that the active oxygen species on the Ce-rich and Sn-rich supports are mainly the lattice oxygen species and the chemisorbed oxygen species, respectively. Although the active oxygen species on the Ce-rich supports have higher intrinsic activity, the active oxygen species on the Sn-rich supports have better mobility. It leads to an interesting phenomenon that the change trend of the activity of the Pd/Sn1-xCexO2 catalysts with temperature is consistent with that of their supports. Compared with the Ce-rich supports and the corresponding supported Pd catalysts, the catalytic activity of the Sn-rich supports and the corresponding supported Pd catalysts increased faster with the increase of temperature.