The invention belongs to the field of application of agricultural machinery, in particular to a core working part knotting machine of a small bale baler. The knotting machine has the function of knotting rope ends at both ends of a baling rope for enveloping a compressed material into a rope knot and mainly comprises a knotting machine frame body, a bevel pinion, a knotting pincer shaft assembly, a support seat, a rope gripper, a rope cutting blade and a planetary gear mechanism. The knotting machine is used together with the small bale baler; when the bale reaches the preset bale length, a baling mechanism clutch is combined. A baling needle leads the baling rope to the knotting machine; under the drive of the bevel pinion, a rope clamping disk and a pincer nozzle rotate in the opposite directions to clamp and wind the rope; the pincer nozzle continuously rotates, an upper claw idler wheel rolls on a cam track, an upper claw is forced to expand, and the two baling ropes are led between the upper claw and a lower jaw of the pincer nozzle; the pincer nozzle knots the baling ropes along with the continuous rotation of the pincer nozzle and the rope clamping disk, and the pincer nozzle knots the baling ropes; the rope cutting blade cuts off the baling ropes, the manufactured knot is naturally released, and a knotting process is finished.