The invention relates to a flow battery. The flow frame boards of the flow battery are provided with liquid inlet holes and liquid outlet holes; the front surfaces of the flow frame boards are provided with liquid inlet branch flow channels and liquid outlet branch flow channels; one end of each liquid inlet branch flow channel is communicated with the liquid inlet holes, and the other end thereof is communicated with the inner frames of the flow frame boards; one end of each liquid outlet branch flow channel is communicated with the liquid outlet holes, and the other end thereof is communicated with the inner frames of the flow frame boards; the flow frame boards are alternately arranged according to a mode of front surface to front surface and back surface to back surface in sequence; an ion exchange film is clamped between the opposite front surfaces of the adjacent flow frame boards; a current-conducting plate is clamped between the opposite back surfaces of the adjacent flow frame boards; the edge of the inner frame of each flow frame board is provided with an annular chamfer; the current-conducting plate is arranged on the annular chamfer; and electrodes are arranged in the inner frames of the flow frame boards. The flow battery has fewer components, simple and compact structure, easy processing, convenient assembly, small thickness, small volume, small internal resistance, good transfer and diffusion effect of electrolyte, small self discharge current, big power density, high energy efficiency and low cost and can realize big-power and large-scale application.