The invention relates to the technical field of flow batteries, and more particularly to a pressure balance device and method for a vanadium battery liquid storage tank. The device comprises an inertgas storage device, a first gas inlet pipeline and a second gas inlet pipeline, wherein the inert gas storage device is communicated with a vanadium battery negative electrode liquid storage tank through the second gas inlet pipeline; the vanadium battery negative electrode liquid storage tank and a vanadium battery positive electrode liquid storage tank are communicated through the first gas inlet pipeline; the inert gas storage device is used for transporting the inert gas to the vanadium battery negative electrode liquid storage tank through the second gas inlet pipeline, and the first gasinlet pipeline is used for transporting the gas in the vanadium battery negative electrode liquid storage tank to the vanadium battery positive electrode liquid storage tank. Thus, pressure balance inthe vanadium battery liquid storage tank can be kept constantly.