The utility model relates to an automatic regulating brake gap wedge type mechanism, which is used for drum type braking device. A vertical hole I with a communicative horizontal hole II thereof is arranged inside the shell; the terminal cover is connected inside with the hole I. On the exterior side of the hole II, a pyramid surface P is arranged, the interior side of which is provided with a driving ring with a protective cover arranged on the exterior side. One terminal of driving ring with spring leans against the interior side of the protective cover and belongs to the terminal of driving ring with the spring, and the other terminal leans against the exterior side of the driving ring, thereby pressing the driving ring onto the pyramid surface P adjacent to the communicative hole II; a piston that is connected with the communicative through sliding, and with a roller packing block in pin connection at the back and a spiral tooth being arranged in the front, is arranged inside the spiral slot in the interior side of the driving device, with a space delta being left between the spiral tooth and the slot. A gasket is connected with the upper part of the wedge, with two rollers being in pin connection symmetrically with the lower part. A compressed spring is arranged between the gasket and the terminal cover. The lower side of the wedge block runs into the hole I on the lower part of the protective cover. The roller is arranged on the site corresponding to the rolling cylinder propelling block. The adjustment bolt is in spiral connection with the screw hole at the center of the piston, and the front part of the adjustment hole is connected with the screw braking hoop.