Field-assisted electrocatalytic reactions are demonstrated to be sufficient strategies in enhancing the electrocatalyst activities for oxygen evolution reaction (OER). Here, we report the in-situ magnetic field enhanced electrocatalytic activity in ferromagnetic FeCo₂O₄ nanofibers. Our results demonstrate that the overpotential of FeCo₂O₄ nanofibers at 10 mA cm⁻² shows a left-shift of 40 mV for the OER by applying an external magnetic field, and no obvious change has been observed in the non-ferromagnetic-order Co₃O₄ nanofibers. Calculation results indicate that there are more overlaps between the density of states for Co 3d and O 2p by applying an external magnetic field. Accordingly, the spin hybridization of 3d-2p and the kinetics of spin charge transfer are optimized in ferromagnetic FeCo₂O₄, which can promote the adsorption of oxygen-intermediates and electron transfer, significantly improving its electrocatalytic efficiency. What’s more, the maximum power density of the FeCo₂O₄ nanofibers based Zn-air battery (ZAB) increases from 97.3 mW cm⁻² to 108.2 mW cm⁻² by applying an external magnetic field, providing a new idea for the application of magnetic cathode electrocatalysts in ZABs.