An electrode structure of a vanadium redox flow battery is disclosed, which includes a proton-exchange membrane, two graphite papers, two graphite felt units, two pads, two graphite polar plates, two metal plates and a lock-fixing device which are symmetrically stacked in sequence from center to outside. wherein each graphite polar plate has the flow channels with a grooved structure, and each graphite felt unit is embedded in the flow channels of one of the graphite polar plates, and then the graphite felt units are covered by the graphite papers such that the different electrolytes flow in their corresponding flow channels. The storage tanks of vanadium electrolyte are connected through the connection pipelines, and the redox reaction is performed through the flows of the vanadium electrolyte. The electrode structure of the vanadium redox flow battery can be stacked for forming a large-scale electrode structure to increase the electrical power.