NOVELTY - The device comprises a hollow tube, and a filling protection sleeve (8), which is paved with an anti-seepage layer in garbage field low-lying with a certain slope. A garbage stacking layer of a certain thickness is provided for the filling protection sleeve. The hollow tube is retained into a sewage collecting pipe (5). The garbage stacking of middle, upper and lower uppers are provided in the same direction in turn distributed with the hollow tube for the filling protective sleeve. The upper layer is guided with the hollow tube for the filling protective sleeve.    USE - The device is useful for collecting a methane gas.    ADVANTAGE - The device is capable of effectively and economically collecting the methane gas with high productivity in an environmentally-friendly manner.    DETAILED DESCRIPTION - The device comprises a hollow tube, and a filling protection sleeve (8), which is paved with an anti-seepage layer in garbage field low-lying with a certain slope. A garbage stacking layer of a certain thickness is provided for the filling protection sleeve. The hollow tube is retained into a sewage collecting pipe (5). The garbage stacking of middle, upper and lower uppers are provided in the same direction in turn distributed with the hollow tube for the filling protective sleeve. The upper layer is guided with the hollow tube for the filling protective sleeve. The upper layer is pulled with the filling protective sleeve on a pile cap. The hollow tube is retained into a marsh gas collecting pipe (6). The sewage collecting pipe is connected with the uniform collecting pipe with sewage to purifying a tank. The marsh gas collecting pipe is provided on two ends. The sewage collecting pipe is continuously discharged.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a device for collecting a methane gas.    Leakproof layer (2)    Covering layer (4)    Sewage collecting pipe (5)    Marsh gas collecting pipe (6)    Filling protection sleeve. (8)