The invention provides a preparation method of a superfine metal fiber and the superfine metal fiber prepared by the preparation method. The preparation method comprises the following steps: polymer resin is filled with metal powder, of which the fusion point is not lower than the fusion point or the softening temperature of the polymer resin, and when the blend extruded by an extruding machine passes through a neck mould of the extruding machine, the blend is stretched directly and longitudinally to obtain polymer/metal complex fiber containing the superfine metal fiber; and during the preparation process, the metal powder is extended in situ to form the superfine metal fiber owing to factors such as interaction between polymer and metal, and then polymer matrix in the complex fiber is dissolved so as to separate the superfine metal fiber from the complex fiber. The preparation method has simple steps and is low in cost, and the superfine metal fiber prepared by the preparation method is adjustable in diameter. During the preparation process of the superfine metal fiber, metal is always packed in a polymer so as to be free from oxidation and corrosion caused by the external environment.