The invention discloses a large-aperture double-plate flat valve. The large-aperture double-plate flat valve comprises a valve body, wherein the inside of the valve body is provided with a valve cavity and double valve plates which can vertically move along the valve cavity to open or close the flat valve; the double valve plates do not have flow way holes; the double valve plates and the valve cavity are sealed by a valve seat; a limiting block of which the cross section is arc-shaped is arranged below the double valve plates; the top surface of the limiting block is matched with the bottom surfaces of the double valve plates, and it ensures that the valve plates can sit on the limiting block in a sealing manner; a wedge-shaped ring which is positioned between the double valve plates is arranged on the limiting block; two side surfaces of the wedge-shaped ring are ring surfaces which are inclined from top to bottom; inclined surfaces from bottom to top are arranged on the inner sidesof the double valve plates; the limiting block has a structure which is small in top and large in bottom; one end of the valve seat is propped against the double valve plates and one side of the upperportion of the limiting block; a boss is arranged between the upper portion and the lower portion of the limiting block; the boss is positioned below the bottom surface of the valve seat; the limiting block and the valve body cooperate to position the valve seat; annular grooves are separately formed in the two side surfaces, which cooperate with the double valve plates, of the valve body; and asealing ring is arranged in each annular groove.