The utility model discloses a transmission final-state pin shaft reducer, which comprises a hydraulic motor and a planetary gearbox, wherein the planetary gearbox is connected with the hydraulic motor and driven by the hydraulic motor. The torque output end of the hydraulic motor is connected with the shaft end of a first-stage sun gear in a gear shaft structure penetrating through a second-stage sun gear in the gearbox, a first-stage planetary gear fixed on a first-stage planetary frame through a planetary frame shaft column is respectively meshed with the first-stage sun gear and a casing of the gearbox, and the second-stage sun gear is connected with the first-stage planetary frame and meshed with the second planetary gear. The second planetary gear fixed on a support through a pin shaft is meshed with the casing of the gearbox and the second-stage sun gear, and a second-stage planetary frame is fixed on the support through a bolt, the casing of the gearbox and serving as the torque output end is movably connected with the support to form an outer structure of the planetary gearbox. The transmission final-state pin shaft reducer utilizes the pin shaft and the bolt to replace a fixing connection way of the planetary frame and the planetary gears in the original reducer, is simple in structure and easy to assemble, and saves production cost and production time.