NOVELTY - A methane pool with internal gasbag comprises pool, gas transmission pipeline, feed pipe, and pool top cover; where the pool comprises cuboid fermenting pool (1), cuboid hydraulic pressure room (2), and ladder-like passage (9) connected to the fermenting pool (1) and hydraulic pressure room (2); one side of the fermenting pool (1) is equipped with gas transmission pipeline (4) and feed pipe (5); the top of the gasbag (7) is installed with a gasbag discharging pipe (8) which extends from the gas transmission pipeline (4) and is connected to users.    USE - The methane pool with internal gasbag is used for industrial application.    ADVANTAGE - The methane pool with internal gasbag separates the work of the pool from the work of the pool air tightness. The pool air tightness is finished by the gasbag, making construction process of the pool simple. The methane pool can be repeatedly used by changing gasbag, thus the constructing cost becomes lower.    DETAILED DESCRIPTION - A methane pool with internal gasbag comprises pool, gas transmission pipeline, feed pipe, and pool top cover; where the pool comprises cuboid fermenting pool (1), cuboid hydraulic pressure room (2), and ladder-like passage (9) connected to the fermenting pool (1) and hydraulic pressure room (2); top of the fermenting pool (1) and hydraulic pressure room (2) is equipped with two or more opened movable top covers (3); one side of the fermenting pool (1) is equipped with gas transmission pipeline (4) and feed pipe (5); four corners in the fermenting pool (1) are all equipped with gasbag brackets (6); square pentahedral gasbag (7) supported by the gasbag bracket (6) is reversely buttoned in the fermenting pool (1); five surfaces of the gasbag (7) closes to the tetrahedral pool walls and top cover (3) of the fermenting pool (1) respectively; the top of the gasbag (7) is installed with a gasbag discharging pipe (8) which extends from the gas transmission pipeline (4) and is connected to users.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of the methane pool with internal gasbag.    Fermenting pool (1)    Hydraulic pressure room (2)    Top cover (3)    Gas transmission pipeline (4)    Feed pipe (5)