The invention discloses a device for fixing a transportation tool of a small conveyer line buffer module. The device comprises a supporting frame, a pneumatic system, a side baffle, a movable horizontal plate, a movable left baffle, a movable right baffle, a fixed baffle, a roller system and a piston rod, wherein the movable left baffle and the movable right baffle are installed on the front side of the movable horizontal plate, the movable left baffle is a rectangular block, a wedge angle is formed on the front section of the movable right baffle, a rectangular block is arranged at the rear end of the movable right baffle, and the height of the movable left baffle and the height of the movable right baffle are smaller than the thickness of the transportation tool; the distance between the inner side of the rectangular block of the movable left baffle and the inner side of the rectangular block of the movable right baffle is equal to the length of the transportation tool; the uppermost surface of the roller system and the upper surface of the supporting frame are located in the same horizontal plane. After the transportation tool touches a roller movement stop proximity switch, the roller system stops operation, and then primary positioning is achieved; the piston rod pushes the movable horizontal plate to achieve accurate positioning through the movable left baffle and the movable right baffle; the movable horizontal plate is further pushed, the transportation tool approaches the fixed baffle, and then fixation is achieved. The device is simple in structure and convenient to implement, and transportation tool fixing accuracy is high.