The utility model discloses a clamping plate for clamping and loosening a screw. The clamping plate comprises a plate body (1), assembling through holes (2) distributed in an array mode are formed in the plate body (1), each assembling through hole (2) A is composed of a small round hole portion (6) in the left side, a large round hole portion (7) in the right side and a connecting portion (8) communicated with the small round hole portion (6) and the large round hole portion (7), and the left edge and the right edge of the plate body (1) are respectively provided with a vertical clamp (9). The clamping plate has the advantages that the screw is clamped and loosened through conversion of the small hole combination and the large hole combination, and therefore the state of clamping the screw and the state of loosening the screw to allow the screw to penetrate through a gasket in a sleeved mode can be converted, a mounting and clamping device is provided for batched screws to penetrate through elastic gaskets and flat gaskets in a sleeved mode, the problems that the screws penetrate through the elastic gaskets and the flat gaskets manually one by one in the sleeved mode, time and labor are wasted, the penetrating and sleeving efficiency is low, and fatigue is probe to occurring can be solved, and the screws can fast penetrate through the elastic gaskets and the flat gaskets fast in the sleeved mode.