The invention provides an anti-fall reduction gear for protection of a vertical circulating stereo parking garage, and belongs to the field of stereo parking lots. The anti-fall reduction gear comprises an annular support, a sliding groove, two baffles, a chain, hinge pins, multiple swing rod stopping mechanisms, swing rod driving mechanisms, a sensing mechanism and a controller, wherein the sliding groove with an inward opening is formed in the support, the baffles are arranged on the two sides of the inner end face of the sliding groove and extend toward the inner side of the opening of thesliding groove, the chain is arranged in the sliding groove and is in sliding cooperation with the sliding groove, the hinge pin is arranged on the chain, the swing rod stopping mechanisms are arranged around the support and used for supporting the two ends of the hinge pin, the swing rod driving mechanisms are used for driving the swing rod stopping mechanisms to swing around hinge shafts of theswing rod stopping mechanisms and the sliding groove, and the sensing mechanism is in contact with the chain and is used for sensing whether or not the chain fractures. When fracturing of the chain fractures is sensed, the anti-fall reduction gear for protection of the vertical circulating stereo parking garage controls the swing rod driving mechanism to act rapidly in a short time, blocks the sliding groove and can stop the hinge pins closest to the swing rod stopping mechanisms from falling down, and thus the usage safety is improved.