The invention discloses a dual-layer mechanical grate type garbage gasifying incinerator and a dual-boiler power generation system thereof. The dual-layer mechanical grate type garbage gasifying incinerator comprises a dual-layer garbage gasifying incinerator, a boiler system and a circulating air supply system, wherein the dual-layer garbage gasifying incinerator comprises a feeding hopper, a gasification furnace and a burnout furnace; the burnout furnace is positioned directly under the gasification furnace; the feeding direction of the burnout furnace is opposite to the feeding direction of the gasification furnace, and flue gas outlets are formed in the upper end of the gasification furnace and the upper end of the burnout furnace; the boiler system comprises a boiler body a, and a boiler body b, wherein the boiler body a is provided with a cyclone-combustion chamber, a furnace chamber a, and a furnace chamber b; a flue gas inlet of the cyclone-combustion chamber is connected with a flue gas outlet of the gasification furnace; the boiler body b is provided with evaporators b, superheaters b, and water-cooled walls b, which are arranged on a flue gas pipeline in a sleeving manner, wherein the superheaters are arranged in the furnace chamber a, the evaporators are arranged in the furnace chamber b, and the superheaters and the evaporators are arranged in a furnace chamber d; steam drums are arranged at the top ends of the two boiler bodies.