The invention provides a preparation method of a vanadyl sulfate crystal and application of the vanadyl sulfate crystal.The method comprises the following steps that vanadium pentoxide and sulfuric acid with the concentration of 15 mol/L-20 mol/L are added into a reaction kettle and mixed to be uniform; the reaction kettle containing vanadium pentoxide and sulfuric acid with the concentration of 15 mol/L-20 mol/L is put into a sealed reactor, reduction gas is introduced into the sealed reactor, the temperature is increased, and a reduction reaction is conducted; after the reduction reaction is completed, the reaction kettle is taken out, and the vanadyl sulfate crystal is obtained.The high-purity vanadyl sulfate crystal is prepared directly through a reduction method, evaporation crystallization treatment is not needed in the whole technology process, operation is easy, the reaction condition is mild, the cost is low, and the content of foreign ions in vanadyl sulfate electrolytes prepared from the high-purity vanadyl sulfate crystal is low and lower than 10 ppm.