The invention relates to a special clamp for realizing multi-point clamping. The special clamp comprises a clamp body, wherein a piston rod which is in horizontal arrangement and can move is arranged in the clamp body, the lower side of one end of the piston rod is provided with an inclined surface, the other end of the piston rod is provided with a piston, a guide sleeve with the Y-shaped cross section is arranged in the clamp body and under a position, provided with an inclined surface, of the piston, a spring sleeve, a spring and a press block which can vertically move are sequentially arranged in the guide sleeve from top to bottom, a rolling post is arranged between the spring sleeve and the inclined surface, the two sides of the rolling post are provided with position limiting rings, the lower end of the press block is provided with three press claws in circumferential distribution, and the three press claws can extend out of the guide sleeve for tightly pressing a workpiece. The special clamp has the advantages that through hydraulic driving, three press claws arranged on the press block are simultaneously in contact with the workpiece, the installing and clamping rigidity of the workpiece are improved, and the stability and the reliability of the installation and clamping are improved.