The invention provides a clamping and fixing device for clamping a long nozzle in a ladle pouring system, which comprises a trunnion ring which is sheathed on the long nozzle and supports the long nozzle and a clamping block, wherein trunnion ring walls at the upper part and the lower part of the trunnion ring are respectively provided with a first through hole and a second through hole, and outer side of the trunnion ring is provided with a fixed support; and the clamping block can be rotatably hinged on the fixed support, and both ends of the clamping block respectively pass through the first through hole and the second through hole and extend along the radial direction of the trunnion ring. In the invention, the clamping block is added at the outer side of the trunnion ring, and both ends of the clamping block can be in contact with the outer wall of the long nozzle inserted in the trunnion ring through the through holes in the trunnion ring wall. When the long nozzle is inserted in the trunnion ring, the external surface of the long nozzle extrudes the upper end of the clamping block under the action of self gravity to rotate the clamping block; and when the long nozzle is completely inserted in the trunnion ring, the upper end and the lower end of the clamping block are in close contact with the outer wall of the long nozzle simultaneously to clamp and fix the long nozzle so as to prevent steel leakage at the joint of the long nozzle and a sliding plate as a result of the inclination of the long nozzle.