NOVELTY - A portable anaerobic fermentation device for a methane tank, provided with one subsidiary methane tank and at least two methane tanks, where the methane tank is provided with an inflow water guiding pipe, a water flow hole of the methane tank, and a residue discharge hole on the tank bottom; water flow hole; a methane collecting pipe; a check hole and a methane collecting hole; water flow hole and water outlet; a fixed pipe, a moveable pipe, a T-shaped joint and a straight joint.    USE - The portable anaerobic fermentation device is useful for a methane tank (claimed) for treating livestock and poultry breeding wastewater.    ADVANTAGE - The portable anaerobic fermentation device for a methane tank can be efficiently applied in treating livestock and poultry breeding wastewater.    DETAILED DESCRIPTION - A portable anaerobic fermentation device for a methane tank, provided with one subsidiary methane tank and at least two methane tanks, where the methane tank is provided with an inflow water guiding pipe, a water flow hole of the methane tank, and a residue discharge hole on the tank bottom; wastewater flows into the methane tank through the inflow water guiding pipe and is discharged through water flow hole of the methane tank; water flow hole of the methane tank is connected with the subsidiary methane tank; the wastewater discharged from water flow hole of the methane tank flows into the subsidiary methane tank and then is discharged outwards from a water outlet of the subsidiary methane tank; and methane is collected by a methane collecting pipe; an arch side of the methane tank is arranged on the upper part of the methane tank; a check hole and a methane collecting hole are arranged on the arch side of the methane tank; water flow hole and water outlet are arranged on the methane tank above the arch side of the methane tank; a fixed pipe, a moveable pipe, a T-shaped joint and a straight joint are arranged between the methane tank and the subsidiary methane tank; the subsidiary methane tank is connected with the methane tank through water flow hole; the subsidiary methane tank discharges water through water outlet of the subsidiary methane tank; the outflow from water outlet of the subsidiary methane tank is discharged from water outlet of the methane tank after passing through the arch side of the methane tank via water flow hole; the residue discharge hole on the tank bottom as well as the residue discharge hole on the subsidiary methane tank is connected with a valve of a residue discharge pipe; bottom biogas residue of the methane tank and the subsidiary methane tank is discharged by the valve of the residue discharge pipe through the residue discharge hole on the bottom of the methane tank and the residue discharge hole on the bottom of the subsidiary methane tank.