The invention discloses an electrorheological fluid clamping tool for a light and low-noise gearbox. The electrorheological fluid clamping tool is used for positioning and clamping the end face of thegearbox in the machining process, the tool comprises a base, the base is provided with a workpiece bearing plate perpendicular to the base, a through hole used for mounting and demounting the workpiece is formed in the middle of the workpiece bearing plate, protruding positioning blocks are arranged on the inner wall of the through hole, flexible fluid bag storing grooves are formed in the positions, between the positioning blocks, of the inner wall of the through hole, flexible fluid bags are arranged in the storing grooves and connected with a cylinder body through guiding pipes, the cylinder body is internally provided with a piston, the space, at one end of the piston, inside the cylinder body, the guiding pipes and the flexible fluid bags constitute an accommodating chamber for electrorheological fluid jointly, the other end of the piston is connected with a piston driving mechanism, positive electrodes and negative electrodes are arranged at one end of the piston and the inner walls of the flexible fluid bags correspondingly, and the positive electrodes and the negative electrodes are connected with a controller. The electrorheological fluid clamping tool is simple in structure, convenient to use and good in workpiece clamping effect, clamping force in all directions of the workpiece is uniform and firm, and the workpiece can be quickly mounted and demounted.