The utility model discloses a rear-inserting rotary type transplanting mechanism of a deformation oval-cylindrical gear. A shaft end of a central shaft, which extends out of a chain wheel box, is respectively and fixedly provided with a left gear box and a right gear box with same internal structures; the two ends of the central shaft in the gear boxes are respectively provided with a central deformation oval gear; the central deformation oval gears are fixed on the chain wheel box by a left flange and a right flange; the left central deformation oval gear and the right central deformation oval gear drive a middle circular gear to rotate by a left middle deformation oval gear and a right middle deformation oval gear which are fixedly arranged on a left middle shaft and a right middle shaft, wherein the middle circular gear and the left middle deformation oval gear and the right middle deformation oval gear are fixed on the left middle shaft and the right middle shaft; while a left middle cylindrical gear and a right middle cylindrical gear are meshed with a left planetary cylindrical gear and a right planetary cylindrical gear fixedly arranged on a left planetary shaft and a right planetary shaft; and one end of the left planetary shaft and one end of the right planetary shaft, which extend out of the gear boxes, are fixedly provided with planting arm parts. The gear boxes are transmitted by only one group of planetary-system gears relative to the central deformation oval gears so as to drive one planting arm to move. The rear-inserting rotary type transplanting mechanism forms a track with a shape of a ring buckle, a transplanting cavity opening is small and the rice transplanting requirement can be better met.