The invention discloses a reciprocating inverse-pushing type garbage incinerator which comprises a hearth wall body, a hopper device arranged on an upper port of the hearth wall body, a residue falling groove arranged at a lower port of the hearth wall body and a residue discharging machine positioned below the residue falling groove, wherein a reciprocating inverse-pushing type fire grate is arranged in the hearth wall body, a primary air chamber and an ash discharging device are sequentially arranged below the fire grate, a closed rotating shaft fire grate drive device is arranged below thefeeding device; the fire grate comprises a fire grate frame, a plurality of fixed beams used for supporting and fixing fire grate sheets, and a plurality of movable beams used for driving movable fire grate sheets; the fixed beams and the movable beams are arranged on the fire grate frame at intervals laterally, the corresponding fixed fire grate sheets and the movable fire grate sheets are arranged and overlapped at intervals laterally, the fire grate is inclined downwards along the advancing direction of rubbish, the fire grate is divided into 2-6 lines of fire grate units along the direction vertical to the advancing direction of rubbish, and the movable beam of each line of fire grate units is driven by the corresponding primary closed rotating shaft drive device through a movable beam frame. The reciprocating inverse-pushing type garbage incinerator ensures that the rubbish can be effectively conveyed, stirred, loosened, crushed and fully combusted in a process of incinerating the rubbish, and has the advantages of good sealing property, and no air and ash leakage and dropping and permeating phenomena.