Only-Palladium catalysts modified with BaO as a promoter was prepared by an impregnation method. Specific surface area measurements (BET), X-ray diffraction (XRD), CO-chemisorption, H2-temperature-programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the effect of BaO on the physicochemical properties of the catalysts. Their catalytic activities towards methanol, CO and C3H8 conversions were evaluated. The results show that the addition of BaO makes palladium highly dispersed, enhances the amount of active oxygen and promotes the reductive ability. The electron effects between Pd and support is improved. It is favorable for maintaining Pd in a higher oxidized state and transiting Ce4+ to Ce3+, thus accelerating the activated oxygen migration between Pd and the support and consequently increasing the catalytic activities for methanol and CO oxidation at low temperature. The light-off temperature of T50 is lowered by 26 and 21 oC to methanol and CO, respectively compared with unmodified only-Palladium catalysts. Whereas the conversion of C3H8 falls directly because of the higher oxidized Pd2+ and the amount and intensity of the acid sites decreasing obviously