TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In preparing electrolyte for vanadium battery, in step (a), 98% concentrated sulfuric acid is mixed with water into sulfuric acid solution according to a volume ratio being 1:1-3; and then the solution added with the vanadium pentoxide or vanadium trioxide is diluted according to a volume ratio being 1:0.1-1. The vanadium pentoxide as the raw material is formed into positive quadrivalent vanadyl sulfate solution being the anode material for the vanadium battery. The vanadium pentoxide as the raw material is formed into the positive quadrivalent vanadyl sulfate solution; the vanadyl sulfate solution is electrolyzed as the cathode electrolyte to form vanadium electrolyte for the electrolyte electrode in which the positive quadrivalent vanadium and the positive trivalent vanadium each account for 50% of the total vanadium. The vanadium trioxide as the raw material is formed into positive bivalent vanadyl sulfate solution which directly used as the cathode electrolyte of the vanadium battery. The vanadium trioxide as the raw material is formed into vanadyl sulfate solution with positive bivalence and positive tervalence; then the vanadyl sulfate solution is electrolyzed as the anode electrolyte to form the vanadium electrolyte for the electrolyte electrode in which the positive quadrivalent vanadium and the positive trivalent vanadium each account for 50% of the total vanadium. The sulfuric acid is prepared to have a concentration being 3-9 M, to which the vanadium pentoxide or vanadium trioxide is added so that the vanadium concentration in the system after reaction reaches 1.8-5 M. The sulfuric acid is prepared to have a concentration being 4-6 M, to which the vanadium pentoxide or vanadium trioxide is added so that the vanadium concentration in the system after reaction reaches 1.8-3 M. One or more compounds selected from triethanolamine, sulfydryl nicotinic acid, sulfydryl phenol and Gallic acid are added to the mixture. The dosage of the compound is 0.1% to 5% of the overall volume of the system. The dosage of the reducing agent is 0.1-5 g/100 ml in terms of the mass volume ratio of the system.