The invention discloses a damping roller of a downward inclination conveyor. The damping roller is characterized by comprising a barrel and a roller shaft. The roller shaft penetrates the center of the barrel. Bearing blocks are respectively fixed in two end openings of the barrel, and are connected with the roller shaft through bearings. A centrifugal block is arranged on one of the bearing blocks, a brake pad is fixed to the outer wall of the centrifugal block, a brake drum is arranged on the outer side of the brake pad, and the center of the brake drum is fixedly connected to the roller shaft. Besides, a spring is arranged on the centrifugal block, a polyurethane wear layer is arranged on the outer wall of the barrel, bearing caps are respectively fixedly mounted on outer sides of the two bearing blocks, and seal rings are respectively arranged between each of the two bearing caps and the roller shaft. The revolution speed of the damping roller is limited, and thus the belt velocity of the conveyor is limited by friction between the damping roller and a conveyor belt.