The invention discloses a preparation method of an iron-doped vanadium sulfide nano particle electrocatalyst and application of the electrocatalyst as a catalyst for producing hydrogen through electrocatalysis and decomposition of water, and belongs to the field of synthetic technologies and application of catalysts. According to the preparation method, sulfur-enriched organic matter serves as a sulfur source, metal vanadium salt serves as a vanadium source, metal iron salt serves as an iron source, after the sources are uniformly mixed through a mechanical method, Fe-doped vanadium sulfide nano particles are obtained through one-step calcining, and after iron is doped, the hydrogen-producing electrocatalyst with the phase corresponding to V3S4, a uniform chemical composition and an electrocatalytic activity in a whole-PH electrolyte is obtained. The raw materials for synthesis are cheap, the synthesis method is simple, the production cost is low and the controllability is high.