The utility model relates to the technical field of bag folding mechanisms, and particularly discloses a packaging bag folding mechanism which comprises a base, symmetrical electric push rods are fixedly installed on the two sides of the base, symmetrical movable openings are formed in the base, movable blocks are arranged on the movable openings in a sliding mode, and the movable blocks are connected with the electric push rods in a sliding mode. The ends of output shafts of the electric push rods are fixedly installed on the side edges of movable blocks correspondingly, frames are arranged on the movable blocks correspondingly, movable plates are hinged to the frames correspondingly, a transverse plate is arranged over the base, symmetrical inclined plates are fixedly installed on the two sides of the transverse plate, and the top edges of the movable plates are hinged to the side edges of the tops of the inclined plates correspondingly. According to the packaging bag folding mechanism, the packaging bag folding effect can be improved, the phenomenon that folding marks are not clear is reduced, and the packaging bag folding mechanism is simple in overall structure and high in practicability.