The invention discloses production technology and system of vanadium redox battery electrolyte, and belongs to the technical field of vanadium redox battery preparation. The production technology comprises the following steps: (1) adding vanadium pentoxide into a sulfuric acid solution, and stirring to obtain suspension slurry; (2) introducing liquid-state SO2 into the suspension slurry to obtaina mixed solution of VOSO4 and V2(SO4)3; (3) dividing the mixed solution of VOSO4 and V2(SO4)3 into two parts which are separately added into an anode region and a cathode region of a diaphragm electrolyzer, wherein positive electrolyte of the vanadium redox battery is obtained in the anode region, and negative electrolyte of the vanadium redox battery is obtained in the cathode region. According to the production technology disclosed by the invention, liquid-state SO2 is adopted as a reducing agent, and the suspension slurry prepared from sulfuric acid and vanadium pentoxide is directly subjected to liquid-phase reduction in a pressure reaction kettle; then, the positive and negative electrolyte of the vanadium redox battery is prepared in one step by the diaphragm electrolyzer while impurity elements are not introduced, byproducts are avoided, the reaction process is stable and efficient, the raw materials are widely available, the flow is simple and industrial production is easy to implement.