The invention discloses an incinerator automatic ash discharging system. The incinerator automatic ash discharging system comprises an incinerator, wherein a slag discharging opening is formed in thelower part of the incinerator; the system further comprises an electric hoist, a pressure sensor, a slag bucket and a slag bucket carrying track; a cover plate capable of rotating in the vertical direction is arranged at the slag discharging opening, the pressure sensor is connected to the cover plate and is used for detecting the material pressure borne by the cover plate, the electric hoist is connected to the end of the cover plate and drives the cover plate to rotate, so that the slag discharge opening is closed or opened; and the slag bucket is used for loading materials discharged by theincinerator, a slag bucket limit switch is arranged at the position, corresponding to the slag discharge opening, on the carrying track, and the slag bucket is driven by a transmission chain to horizontally move on the carrying track. When the incinerator is subjected to the slag discharging operation, the slag bucket does not need to be manually aligned to the bottom cover of the incinerator, and meanwhile, the whole process of slag discharging is automatically completed. The working efficiency of the slag discharging of the incinerator is greatly improved, a large amount of working time issaved, and the working intensity is reduced.