The invention discloses a ZnFe2O4 nitrogen-doped nanometer fiber composite electrode material and a preparation method thereof. The composite material comprises nitrogen-doped carbon nanometer fiber and ZnFe2O4 ultramicro nanoparticles embedded into the nitrogen-doped carbon nanometer fiber. The preparation method is an in-situ growth process and comprises the steps of firstly, mixing a ferric salt, a zinc salt and polyacrylonitrile in a dimethyl formamide solution according to different proportions; secondly, preparing a ZnFe2O4/nitrogen-doped carbon nanometer fiber precursor by an electrospinning technology; and finally, performing stabilization, carbonization and low-temperature induction on the precursor to obtain the ZnFe2O4 nitrogen-doped nanometer fiber composite electrode material.The ZnFe2O4/nitrogen-doped nanometer fiber composite electrode material prepared by the method shows high specific capacity, long cycle lifetime and favorable rate performance when used as a supercapacitor electrode material. The method has the characteristics of simple process, low cost, high controllability, industrial production on a large scale and the like.