A double-plate gate valve, comprising a valve body, a valve cover, a valve stem, a guide plate, a goggle plate assembly, a diversion hole assembly, a disc spring assembly and a valve plate and wedge assembly, wherein the guide plate is nested in a valve chamber formed by the valve body and the valve cover; the goggle plate assembly is configured to provide mounting support for the diversion hole assembly and the valve plate and wedge assembly in the valve chamber, the goggle plate assembly is allowed to move along with the diversion hole assembly and the valve plate and wedge assembly in the valve chamber, and floating seals are formed at a contact surface between the diversion hole assembly and the guide plate, and at a contact surface between the valve plate and wedge assembly and the guide plate; the diversion hole assembly is adjustable, that is, a face-to-face distance and a sealing force between a sealing surface of the diversion hole assembly and a sealing surface of the valve body are adjustable, to allow a straight through pipe to be formed and an elastic seal between the diversion hole assembly and a valve seat to be formed in a case that the valve is fully opened; the disc spring assembly is configured to overcome friction forces of the valve plate and wedge assembly and the diversion hole assembly during a closing process of the valve; and the valve stem is configured to transmit actuating forces during opening and closing processes of the valve; wherein the diversion hole assembly comprises an adjustable diversion hole structure, adjusting bolts, disc springs A, disc spring gaskets, force-adjustment nuts, locking nuts, distance-adjustment nuts, packing A and a lower-flange packing gland; and wherein the adjustable diversion hole structure comprises an upper flange, a lower flange and a circular guide tube; the upper flange is fixedly connected with the circular guide tube, slots are uniformly provided at a side edge of the upper flange, and each of the adjusting bolts is mounted in a corresponding slot; a disc spring A, a disc spring gasket, a force-adjustment nut, a locking nut and a distance-adjustment nut are sequentially mounted on the adjusting bolt; the disc spring A is in contact with a lower surface of the slot, and is pressed against the lower surface of the slot by the disc spring gasket and the force-adjustment nut; the packing A is filled between the lower flange and the circular guide tube, and the packing A is pressed by the lower-flange packing gland, to ensure a seal between the lower flange and the circular guide tube; the distance-adjustment nut is in contact with the lower-flange packing gland; and the lower flange is fixedly connected with the lower-flange packing gland. the guide plate is nested in a valve chamber formed by the valve body and the valve cover; the goggle plate assembly is configured to provide mounting support for the diversion hole assembly and the valve plate and wedge assembly in the valve chamber, the goggle plate assembly is allowed to move along with the diversion hole assembly and the valve plate and wedge assembly in the valve chamber, and floating seals are formed at a contact surface between the diversion hole assembly and the guide plate, and at a contact surface between the valve plate and wedge assembly and the guide plate; the diversion hole assembly is adjustable, that is, a face-to-face distance and a sealing force between a sealing surface of the diversion hole assembly and a sealing surface of the valve body are adjustable, to allow a straight through pipe to be formed and an elastic seal between the diversion hole assembly and a valve seat to be formed in a case that the valve is fully opened; the disc spring assembly is configured to overcome friction forces of the valve plate and wedge assembly and the diversion hole assembly during a closing process of the valve; and the valve stem is configured to transmit actuating forces during opening and closing processes of the valve; wherein the diversion hole assembly comprises an adjustable diversion hole structure, adjusting bolts, disc springs A, disc spring gaskets, force-adjustment nuts, locking nuts, distance-adjustment nuts, packing A and a lower-flange packing gland; and wherein the adjustable diversion hole structure comprises an upper flange, a lower flange and a circular guide tube; the upper flange is fixedly connected with the circular guide tube, slots are uniformly provided at a side edge of the upper flange, and each of the adjusting bolts is mounted in a corresponding slot; a disc spring A, a disc spring gasket, a force-adjustment nut, a locking nut and a distance-adjustment nut are sequentially mounted on the adjusting bolt; the disc spring A is in contact with a lower surface of the slot, and is pressed against the lower surface of the slot by the disc spring gasket and the force-adjustment nut; the packing A is filled between the lower flange and the circular guide tube, and the packing A is pressed by the lower-flange packing gland, to ensure a seal between the lower flange and the circular guide tube; the distance-adjustment nut is in contact with the lower-flange packing gland; and the lower flange is fixedly connected with the lower-flange packing gland.