The invention discloses a circulating gas combustion supporting garbage treatment system. A second furnace body serves as an auxiliary furnace body of a first furnace body; the heat treatment and the combustion process are separated in the second furnace body to improve the combustion efficiency in the second furnace body; an air feeding port is formed in a heat treatment chamber of the second furnace body, and gas insufficiently burnt in the first furnace body is leaded to the bottom of the heat treatment chamber to help primary combustion of garbage at the bottom of the heat treatment chamber, so that the garbage in the heat treatment chamber can be guaranteed in a precombustion state when entering a high-temperature incineration cavity, and the combustion efficiency in the high-temperature incineration cavity is further improved; the gas in the heat treatment chamber is collected through a circulating gas collecting mechanism, and is fed in the high-temperature incineration cavity for thorough combustion by a circulating gas channel in a feeding device; and final tail gas in the high-temperature incineration cavity is returned into the first furnace body for auxiliary heating, so that the combustion efficiency of the garbage in the first furnace body is improved.