The utility model discloses an automatic fixture of cartoning machine, comprises a first support and a second support, the inboard movable conveyer belt that has cup jointed of first support and second support, the medicine bottle has been placed by the upper surface center department of conveyer belt, the opposite face both ends of first support and second support and the one end fixed connectionof telescopic link, the other end fixed mounting of telescopic link has adjustable fender, the standing groove has all been opened to adjustable fender's opposite face, the inside longitudinal movement of standing groove installs the pivot, and through all being connected through telescopic link and screw rod with the opposite face of first support and second support at adjustable fender, the telescopic link plays and supports and the guide effect, and the screw rod can drive the adjustable fender back -and -forth movement, and the not medicine bottle of equidimension is convenient for be fitfor by the command range, and there is the gyro wheel inside of opening some standing grooves through the opposite face at adjustable fender through pivot movable mounting, firstly plays limiting displacement, secondly plays and normally continues to move ahead the effect.