NOVELTY - Constant pressure marsh gas pool comprises a fermentation room (1), a gas storage chamber (2), the first control device and the second control device. The fermentation room of the first cover body is closed. The gas storage chamber of the second cover body is closed. The fermentation room side wall is respectively set with feedstock pipe (11), a discharge pipe (12). The gas storage chamber side wall is set with an upper air outlet pipe. The fermentation room through gas pipe (13) and gas storage chamber are connected. The gas pipe is equipped with electromagnetic valve.    USE - Used as a constant pressure marsh gas pool.    ADVANTAGE - The marsh gas pool has simple structure, has increased use life, and ensures the pressure during combustion.    DETAILED DESCRIPTION - Constant pressure marsh gas pool comprises a fermentation room (1), a gas storage chamber (2), the first control device and the second control device. The fermentation room of the first cover body is closed. The gas storage chamber of the second cover body is closed. The fermentation room side wall is respectively set with feedstock pipe (11), a discharge pipe (12). The gas storage chamber side wall is set with an upper air outlet pipe. The fermentation room through gas pipe (13) and gas storage chamber are connected. The gas pipe is equipped with electromagnetic valve, which is connected with the first control device. The fermentation room is equipped with the first air pressure sensor. The first air pressure sensor and the first control device are connected with the gas storage chamber and is equipped with the second air pressure sensor. The second air pressure sensor and the second control device are connected. The second cover body is installed in moving air chamber. The second cover body through telescopic mechanism and driving mechanism are connected and the driving mechanism and the second control device are connected.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the constant pressure marsh gas pool.    Fermentation room (1)    Gas storage chamber (2)    Feedstock pipe (11)    Discharge pipe (12)    Gas pipe (13)