Abstract: The present invention provides a method for manufacturing a carbon-coated nanometer Fe3O4 for a cathode of a battery. The manufacturing method includes the following steps: dry mixing Fe3O4 and high-purity conductive carbon black, adding the dry-mixed Fe3O4 powder and conductive carbon black into a prepared NaOH solution, adding a prepared NaBH4 solution into the reaction solution, and conducting aging, pure water cleaning, ultrasonic dispersing, filtering, drying, screening, and seal packing. An iron nickel battery which is produced using the manufacturing method for carbon-coated nanometer Fe3O4 for an electrode of a battery provided in the present invention has high capacity per gram, high charging and discharging efficiency and low self-discharging, is capable of being sealed, and has a simple process, high strength and long life.