NOVELTY - Integral structure of methane production-desulfurization-denitrification comprises methane production area-I, three-phase separating area-II, desulfurization-denitrification area-III and a nitrifying water waste storage tank (23). The methane production area-I, comprises a sewage discharging pipe (1), a water inlet pipe (2), a reaction cylinder (3), a sampling pipe (4) and a back flowing pipe. The sewage discharging pipe is mounted at bottom of reaction cylinder. The water inlet pipe, sampling pipe and the back flowing pipe are orderly mounted on wall of reaction cylinder from top to bottom.    USE - Used as an integral structure of methane production-desulfurization-denitrification.    ADVANTAGE - The device: combines methane production with desulfurization and denitrification, and thus it avoids delivery of the generated methane by an air pump; oxidizes sulfurated hydrogen into simple substance sulfur, thus it recycles sulfur resources; and reduces nitrate into nitrogen, and thus it eliminates nitrogen pollution.    DETAILED DESCRIPTION - Integral structure of methane production-desulfurization-denitrification comprises a methane production area-I, a three-phase separating area-II, a desulfurization-denitrification area-III and a nitrifying water waste storage tank (23). The methane production area-I, comprises a sewage discharging pipe (1), a water inlet pipe (2), a reaction cylinder (3), a sampling pipe (4) and a back flowing pipe. The sewage discharging pipe is mounted at the bottom of the reaction cylinder. The water inlet pipe, the sampling pipe and the back flowing pipe are orderly mounted on the wall of the reaction cylinder from top to bottom. The three-phase separating area-II comprises a sewage precipitating chamber, a reverse funnel-shaped three-phase separator and a first gas chamber; and a first overflowing water outlet pipe is mounted on the outer side wall of the sewage precipitating chamber. A methane sampling monitoring pipe is mounted in the outer side wall of the first gas chamber. The desulfurization-denitrification area-III main body comprises a first desulfurization-denitrification cylinder and a second desulfurization-denitrification cylinder which comprises a methane input pipe, a second overflowing water outlet pipe, a second gas chamber, a methane purifying constant pressure pipe, a third gas chamber, a methane collecting pipe, a nitrifying waste water self-flowing pipe, a disk-shaped gas distributor and a sewage funnel. The lower parts of the first and the second desulfurization-denitrification cylinders are respectively provided with a sewage funnel. The upper part of each of the sewage funnel is provided with the disk-shaped gas distributor connected with the methane input pipe. The bottom end of the sewage funnel is connected with the sulfur discharging pipe. The upper end and the lower end of the methane purifying constant pressure pipe are respectively connected with the third gas chamber and the second gas chamber. The two fluids in the upper and the lower desulfurization-denitrification cylinders are communicated by the nitrifying waste water self-flowing pipe, where the methane collecting pipe is mounted on the outer side wall of the first desulfurization-denitrification cylinder, and the second overflowing water outlet pipe is mounted on the outer side wall of the second desulfurization-denitrification cylinder.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the integral structure of methane production-desulfurization-denitrification.    Sewage discharging pipe (1)    Water inlet pipe (2)    Reaction cylinder (3)    Sampling pipe (4)    Nitrifying water waste storage tank (23)