Lithium-oxygen batteries have attracted considerable attention in the past several years due to their ultra-high theoretical energy density. However, there are still many serious issues that must be addressed before considering practical applications, including the sluggish oxygen redox kinetics, the limited capacity far from the theoretical value, and the poor cycle stability. This study proposes a surface modification strategy that can enhance the catalytic activity by loading Fe₃C particles on carbon fibers, and the microstructure of Fe₃C particle-modified carbon fibers is studied by multiple materials characterization methods. Experiments and density functional theory (DFT) calculations show that the discharge products on the Fe₃C carbon fiber (Fe₃C-CF) cathode are mainly Li_2−xO₂. Fe₃C-CF exhibits high catalytic ability based on its promotion of the formation/decomposition processes of Li_2−xO₂. Consequently, the well-designed electrode catalyst exhibits a large specific capacity of 17,653.1 mAh g⁻¹ and an excellent cyclability of 263 cycles at a current of 200 mA g⁻¹.