NOVELTY - A gas fermentation tank, comprises a tank body (1) having cover opening and a cover body (2), and feed inlet, the material is discharged from discharge outlet and air exhaust port, the tank body is provided with heat preservation layer (4) which has settling chamber, the partition wall and gas generating chamber is divided into first gas chamber (14) and second gas generating chamber. The bottom of air chamber communicated with first gas chamber top and second gas chamber is communicated with second at top of gas chamber rises and chamber prevent liquid from cracking materials.    USE - As gas fermentation tank for urban sewage treatment (claimed).    ADVANTAGE - The gas fermentation tank has high space, utilization rate, large gas discharge amount, and discharge the waste residue that is substantially free of gas.    DETAILED DESCRIPTION - A gas fermentation tank, comprises a tank body (1) having cover opening and a cover body (2), and feed inlet (11), the material is discharged from discharge outlet (12) and exhausts the air exhaust port, the tank body of the side wall and the bottom is provided with a heat insulation heat preservation layer (4) which is sequentially provided with a settling chamber (13), the gas chamber (16) rises and the feed inlet and settling chamber at the upper part, the discharge outlet is communicated with upper chamber which is communicated with the gas chamber. The bottom is provided with a partition wall (141) and the gas generating chamber is divided into a first gas chamber (14) and second gas generating chamber (15). The bottom of the air chamber communicated with the top of the first gas chamber top and a second gas chamber is communicated with the second at the top of the gas chamber rises and the bottom of the chamber prevent liquid from cracking materials.    DESCRIPTION OF DRAWING(S) - The figure shows a view of gas fermentation tank.    Tank body (1)    Cover body (2)    Gas exhaust port (3)    Heat preservation layer (4)    Discharge hole (12)    Sedimentation chamber (13)    First gas generating chamber (14)