The invention discloses a clamping device for an irregular metal product. The clamping device comprises a first gear and a second gear which are coaxially arranged. The radius of the first gear is greater than the radius of the second gear. The clamping device further comprises a connecting shaft. The connecting shaft is provided with a rotatable first fan-shaped gear and a rotatable second fan-shaped gear. A gear of the first fan-shaped gear is arranged on the outer side wall and is engaged with the second gear. A gear of the second fan-shaped gear is arranged on the inner side wall and is engaged with the first gear. The tail end of the second fan-shaped gear is connected with a first clamping claw, and the tail end of the first fan-shaped gear is connected with a second clamping claw. The irregular metal product is jointly clamped between the first clamping claw and the second clamping claw. The clamping device is simple in structure, the good fixing and clamping effects can be achieved for the metal product with an irregular structure, and subsequent processing operation is facilitated.