The invention discloses a descending loading conveying device with a speed reducer. The descending loading conveying device comprises a slideway, a conveying belt, a driving roller, a driven roller, amotor and the speed reducer, wherein the slideway comprises an upper end and a lower end; the upper end is arranged at an output port of a production line; the lower end is close to one end of the conveying belt; the slideway is obliquely arranged; the conveying belt is arranged on the driving roller and the driven roller in a sleeving manner; and the speed reducer comprises a box body, a first rotating shaft, a second rotating shaft, a second gear, a third grooved wheel, a telescopic assembly, a second grooved wheel, a first belt, a first bearing, a second bearing, a first air cylinder and asecond air cylinder. According to the descending loading conveying device with the speed reducer, the speed reducer has the speed changing capacity, products enter the conveying belt after sliding down from the slideway, and the running speed of the conveying belt can be adjusted according to the frequency of fallen product packaging boxes.