The invention discloses a double-membrane back pressure valve. The double-membrane back pressure valve comprises a valve body, a bonnet, a valve rod, a force measuring sensor, a spring, membranes, a damper, a display unit and the like and is characterized in that the upper membrane and the lower membrane are separated through a metal support piece to form a middle cavity, the spring and the damperare fixed on the upper membrane through a bottom plate, the upstream position of the lower membrane is provided with a small hole. When the double-membrane back pressure valve is used, a hand wheel is rotated to allow the valve rod to move downwardly, and the valve is closed; when fluid pressure is larger than a set value, the membranes upwardly compress the spring, the back pressure valve is opened, and fluid start flowing; when the fluid pressure is smaller than a set value, the spring pushes the membranes downwardly to close the back pressure valve, and fluid flowing is stopped. The double-membrane back pressure valve has the advantages that by the small hole, the fluid pressure is transmitted into the cavity between the two membranes, the upper membrane is uniformly stressed, the stress of the membranes, the spring and the damper is relatively balanced, and valve movement stability is achieved; by the damper, gentle valve movement is achieved, and disturbance to the flowing is reduced.