The utility model discloses a bar hydraulic pressure rapid clamping device, its characterized in that: rapid clamping device includes cylinder body, cavity, piston, chuck assembly mounting hole, chuck assembly, spring, and chuck assembly includes interior chuck, outer chuck, treats that the pressure bar material passes in following interior chuck, outer chuck and mounting hole cooperation, and be provided with the flange on the outer chuck, the flange lies in the wild card and faces left the end near spring one side, the cylinder body right -hand member is provided with right spacing arch on the cylinder body, be provided with the oiling chamber between the spacing arch in the right side and cylinder body and the piston, be provided with on the cylinder body with the oil inlet and the oil -out of oiling chamber intercommunication. The utility model discloses a hydraulic oil injects the oiling chamber into and drives the piston and move left, and drive the spring and move left with outer chuck this moment, and the chuck was towards being close to the motion of cylinder body the central axis orientation in the cooperation inclined plane that utilizes outer chuck and interior chuck drove, and what interior chuck core was placed in the realization treats that the clamp that the pressure bar expects is tight, vice versa.