NOVELTY - A positive electrolyte preparing method involves reducing a high-valence oxide which is insoluble in water, to a low-valence vanadium ion which is easily soluble in water through redox reaction, utilizing chemical synthesis, preparing vanadium-containing ore by extracting stone coal and vanadium pentoxide to collect vanadium(IV) oxide sulfate as vanadium battery electrolytic liquid, reducing vanadium pentoxide through sulfur oxide, utilizing vanadium pentoxide, sulfuric acid and water as raw material, and carrying out vanadium pentoxide dissolution..    USE - Method for preparing positive electrolyte of an all-vanadium redox flow battery through a chemical synthesis.    ADVANTAGE - The method enables preparing the positive electrolyte with good charge and discharge performance.    DETAILED DESCRIPTION - A positive electrolyte preparing method involves reducing a high-valence oxide which is insoluble in water, to a low-valence vanadium ion which is easily soluble in water through redox reaction, utilizing chemical synthesis, preparing vanadium-containing ore by extracting stone coal and vanadium pentoxide to collect vanadium(IV) oxide sulfate as vanadium battery electrolytic liquid, reducing vanadium pentoxide through sulfur oxide, utilizing vanadium pentoxide, sulfuric acid and water as raw material at room temperature, carrying out vanadium pentoxide dissolution by passing pure sulfuric acid, and pure carbon dioxide to obtain vanadium(IV) oxide sulfate-sulfuric acid solution, followed by performing vanadium pentoxide reduction by using elemental sulfur, and vanadium pentoxide as raw material, mixing vanadium pentoxide powder, heating with concentrated sulfuric acid, utilizing vanadium pentoxide chemical reduction by using sulfur powder, preparing vanadium(III) and vanadium(IV) electrolytic liquid by reacting vanadium pentoxide and vanadium trioxide, and dissolving in sulfuric acid solution under a controlled electric heating stirring to obtain a vanadium (III) and vanadium(IV) mixed solution.