Oxygen carriers (OCs) with typical perovskite structures have attracted attention for use in chemical looping combustion (CLC) owing to their unique tunable structures and excellent performance. Thus, a further improvement in the reactivity and a deep understanding of the kinetic behaviour in CLC are highly desirable for such perovskite OCs. In this study, a series of Sr-doped perovskite-structured CaFeO 3 OCs (denoted as Sr x Ca 1Àx FeO 3 ) were synthesized. The CLC characteristics, kinetic behaviour, and doping mechanism were systematically investigated via experiments and density functional theory (DFT) calculations. The activation energies of Sr x Ca 1Àx FeO 3 OCs with various Sr contents were found to be in the range of 36.6-40.1 kJ/mol and lower than that of CaFeO 3 (62.7 kJ/mol), indicating that the Sr doping enhanced the reactivity of CaFeO 3 . Among the OCs, Sr 0.4 Ca 0.6 FeO 3 , which had the lowest activation energy and the fastest release of lattice oxygen, was regarded as the optimum OC. DFT calculations indicated that the reaction energy barrier of Sr x Ca 1Àx FeO 3 (0.73-1.06 eV) was lower than that of CaFeO 3 (2.18 eV). This suggests that Sr doping and the regulation of the reaction pathways are essential drivers for enhancing the reactivity of Sr x Ca 1Àx FeO 3 , which affects the release of lattice oxygen and the morphological properties of OC particles.