The invention discloses a special fixture for a square swing sieve. The special fixture comprises a dust cover and a box body. A fixing buckle is a U-shaped groove which is formed by oppositely folding a steel sheet to clamp a hanging buckle of a locking buckle. The locking buckle is composed of a locking base, a pin shaft, a spring, a cylinder, a nut and a screw. The side face of the locking base is provided with a pin shaft hole, and the bottom end of the cylinder is in a flat shape, provided with a fixing hole concentric with the pin shaft hole and fixed through the pin shaft; and the screw penetrates out of a round-bead-shaped hanging buckle hole in the head end of a handle and stretches into the cylinder, the end, stretching into the cylinder, of the screw is wound with the spring and fixed to the head of the cylinder through the nut, and the exposed end of the screw is tightly screwed with an inner thread machined in the round-bead-shaped hanging buckle hole in the head end of the handle. By means of the special fixture for the square swing sieve, the problem that the pressing force of the locking buckle is insufficient can be solved, effective sealing between the dust cover and the box body can be achieved, and the special fixture is convenient and reliable to use.