The invention discloses a flue gas treatment system for a garbage treatment furnace. The flue gas treatment system comprises a garbage incineration treatment furnace, a steam and smoke mixing coolingdevice, a sewage circulating device, an induced pipe, a cyclone settlement dust remover and an air exhausting pipe, wherein the garbage incineration treatment furnace comprises a shell, an incineration treatment chamber, a flue gas buffer chamber, a furnace body water cooling chamber and a smoke extracting pipe, and an air inlet extending to the shell is formed in the flue gas buffer chamber; thesteam and smoke mixing cooling device comprises an outer pipe body, a smoke exhausting pipe arranged in the outer pipe body, a cooling spraying nozzle arranged on the outer pipe body above the smoke exhausting pipe, a mixing chamber arranged in the outer pipe body and a steam recycling pipe arranged on the outer pipe body; one end of the steam recycling pipe extends into the mixing chamber and communicates with the mixing chamber, and the other end of the steam recycling pipe communicates with the furnace body water cooling chamber; and the sewage circulating device communicates with the mixing chamber. The flue gas treatment system has the advantages of high-efficient smoke removal and deodorization, garbage and sewage recycling, low manufacturing and operating cost, stable operation andconvenience in maintenance, and ensures continuous safe operation of the garbage treatment furnace.