The chemical looping process is promising for CO2 conversion because of the much higher CO2 conversion efficiency than the photocatalytic and electrocatalytic processes. Conventional oxygen carriers have to include a high content of inert support, typically Al2O3, to avoid sintering, thus leading to a trade-off between reactivity and stability. Here, we propose the use of ion-conductive GdxCe2-xO2-δ (GDC) to prepare the supported oxygen carriers. The resulting Fe2O3/GDC materials achieve both high reactivity and stability. Fe2O3/Gd0.3Ce1.7O2-δ shows high CO productivity (∼10.79 mmol·g-1) and CO production rate (∼0.77 mmol·g-1·min-1), which are twofold higher than that of Fe2O3/Al2O3. The performance remains stable even after 30 cycles. The mechanism study confirmed the rate-limiting role of the oxygen-ion conductivity, and the GDC support enhanced the oxygen-ion conductivity of oxygen carriers during the redox reactions, thus leading to improved CO2 splitting performance. A roughly linear relationship between the oxygen-ion conductivity and CO2 yield is also obtained and verified in our testing conditions. This relation can be used to predict and select oxygen carriers with high CO2 splitting performance.