The invention provides a special clamp for turning a rear brake drum of an automobile. The special clamp comprises a rotary disk; five screw holes and one counterbore are formed in a bearing block, the bearing block is fixed to the right end face of an adjustment arm through bolt connection and tightening connection, both the front and rear parts of the middle of the bearing block are protruding,and thus the thicknesses of the left and right ends of the bearing block are smaller than that of the middle; a first gland is of a stepped shaft structure, counterbores are formed in the first glandfrom right to left and are in interference fit with blind holes in the left end face of a connection block, and the first gland, the connection block, the bearing block and the adjustment arm are fixed together through inner hexagon screws. In the special clamp for turning the rear brake drum of the automobile, an important connection relationship is a double connection mode of bolt connection andtightening connection, thus component connection is prevented from loosening, and the special clamp is long in service life, high in strength, applicable to clamping of hydraulic chucks of various types at the same time and wide in lathe application range; outer circle fixing serves as a main fixing method, feeding of a turning tool in the rear brake drum is not influenced, machining interferencecannot be generated, and the tool cannot be damaged.