Plasma-assisted catalytic decomposition of CO2over CeO2nanocatalysts was investigated in this study. CeO2nanocatalysts with different morphologies (i.e., cube, rod, and hexagon were prepared by hydrothermal method) were evaluated in a dielectric barrier discharge reaction at room temperature and atmospheric pressure. Among the above catalysts, commercial CeO2and quartz sands, CeO2nanorods (CeO2-R) exhibited the highest CO2conversion under an applied voltage of 8 kV. When the discharge voltage was increased to 9 and 11 kV, all CeO2catalysts showed increased CO2conversion with little difference, but when the applied voltage was larger than 11 kV, the difference in catalytic performance became negligible. The better performance of CO2activation over CeO2-R was attributed to the abundant oxygen vacancies on its exposed (110) crystal plane, which was further confirmed by XPS characterization. Oxygen vacancies on CeO2-R led to twice CO2adsorption amount compared with the other CeO2catalysts, and presented a more significant synergistic effect of oxygen vacancies and plasma on CO2decomposition. The CO2molecules adsorbed on oxygen vacancies over CeO2-R were partly activated and more easily decomposed in the plasma, resulting in higher CO2conversion. Meanwhile, the minimum discharge voltage for CO2decomposition over CeO2-R was 5.0 kV, which was 8.3 kV for commercial CeO2due to its lowest oxygen vacancy density. However, due to the higher electron density and increased probability for free CO2splitting under high discharge voltage, most CO2molecules were activated by the plasma alone, thus less catalyst effect was observed.