The behavior of Fe2O3/Al2O3 particles as oxygen carriers (OCs) for CO chemical looping combustion (CLC) under different reaction temperatures (700 °C, 800 °C, 900 °C, and 1000 °C) were tested in a lab-scale fluidized bed and a thermogravimetric analysis (TGA) unit. The results show that the oxygen carrier presents the highest reactivity at 800 °C, even after 30 cycles of redox reaction in a fluidized bed, while more obvious carbon deposition occurred for the case at 700 °C, and agglomeration for the case at 1000 °C. Moreover, the detailed behavior of the prepared Fe2O3/Al2O3 particle was detected in the TGA apparatus at different reaction temperatures. Furthermore, temperature-programming TGA experiments were performed to investigate the influence of different CO concentrations and CO/CO2 concentrations on the reaction between CO and OC during the chemical looping combustion processes. Based on these experimental behaviors of the prepared Fe2O3/Al2O3 during the CLC of CO, the detailed models and electronic properties of the pure and reduced Fe2O3/Al2O3 supported the slabs, CO adsorption, and oxidation, and the decomposition reactions on these surfaces were revealed using density functional theory (DFT) calculations which went deep into the nature of the synergetic effect of the support of Al2O3 on the activity of Fe2O3 for the CLC of CO.