Exploring alternative cathodic catalysts capable of highly catalytic activity is crucial to the expansion of bioelectrochemical systems. Herein, Fe3O4@N-mC is developed as a magnetic cathode catalyst for bioelectroreduction of oxygen. The Fe3O4@N-mC exhibits better electrocatalytic activity, selectivity (four electron transfer pathway), and long-term electrochemical stability in neutral solutions compared to commercial Pt/C catalyst. The microbial fuel cell using Fe3O4@N-mC generates a power density of 1141 mWm-2, which is higher than that of using Pt/C (1022 mWm-2). Furthermore, the decline of power density is much lower in reactor with Fe3O4@N-mC (4 %) than with Pt/C (8 %). With Fe3O4@N-mC, the cell also obtains higher coulombic efficiency (26 %) than that with Pt/C (21.7 %). The outstanding electrocatalytic activity and stability of Fe3O4@N-mC show its great potential to be a favorable substitute to Pt/C catalysts in microbial electrochemical energy devices.