The invention provides a preparation method of a ferroferric oxide/carbon magnetic nanocomposite material. According to the method, with Fe(NO3)3.9H2O as a raw material, chicken feather (chicken feather-CF) as a reducing agent, and ethanol as a solvent, a solvothermal one-step reaction is carried out to obtain the ferroferric oxide/carbon magnetic nanocomposite material. According to the preparation method, under the premise of not adding any reagent (for example, a precipitant, a reducing agent and a catalyst), transformation from an appropriate amount of Fe<3+> to Fe<2+> is ensured by regulating and controlling the amount of CF; the Fe3O4/C magnetic nanocomposite material with good magnetic property can be obtained; and the preparation method has the prominent advantages of being low in cost, short in flow, high in efficiency, simple to operate, environment-friendly and the like.