NOVELTY - Method for generating methane, involves adding dehydrated sludge into reactor, fermenting sludge, separating solid and liquid, adding anaerobic particle sludge into the dehydrated sludge or adding other fermentation resides of other batch, adding waste organic matter of the dehydrated sludge to the fermentation residue, stirring the mixture using electrical machine, obtaining acid from the stirred mixture, obtaining methane from the mixture and discharging the left residues.    USE - The method is useful for generating methane from urban sludge.    ADVANTAGE - The method can be performed cost-effectively.    DETAILED DESCRIPTION - Method for generating methane, involves (a) adding dehydrated material sludge into reactor, obtaining volume of the material higher than the upper edge of rotator by 5-10 cm, fermenting the sludge primarily under anaerobic condition, separating solid and liquid, eliminating supernatant or adding the anaerobic particle sludge into the dehydrated sludge or adding other fermentation resides of other batch, maintaining water content of the material within 76-83% and adhesive force within 40-50 g and adding waste organic matter (5-30 %mass) of the dehydrated sludge to the fermentation residue, where the dosage volume of the anaerobic particle sludge is 1 divide by 5-1 divide by 4, (b) sealing the material inlet, starting the electrical machine to stir the mixture, culturing and domesticating the anaerobic strains, producing heat by stirring the mixture in order to make temperature of the material reach to 30 degrees C or more, where the stirring speed of the electrical machine is 5-15 revolutions per minute (rpm) and the starting stage is 1-3 days, (c) setting the operation of the stirring electrical machine to be batch-type, adjusting speed of the stirring electrical machine to 10-20 rpm, stirring the mixture using the electrical machine for 8-16 hours per day, starting the temperature controller, maintaining the temperature of the material at 35 plus minus 1 degrees C, monitoring water content, pH value and adhesive force of the material, producing acid for 7-10 days, increasing water content of the material by 1-3% and reducing adhesive force of the material by 10-20 g, (d) setting operation of the electric machine to be batch-type, adjusting speed of the stirring electrical machine to 20-40 rpm, stirring the mixture for 8-16 hours per day, increasing start and stop frequency of the stirring electrical machine in order to make mediate product disperse and the produced air overflow, operating the temperature controller continuously, maintaining the temperature of the material in the reactor at 35 plus minus 1 degrees C and adjusting pH value of the material in the methane producing stage in order to make pH value of the material to 6.6-7.5, where the stage for producing methane is 10-15 days, and (e) using 1/4-1/3 residues of the fermentation inoculating material for next time and discharging the left residues. An INDEPENDENT CLAIM is included for device for generating methane by dry anaerobic digestion of urban sludge and organic matter, which comprises bearing and bearing supporting seat, seal set, external spiral ring band, fermentation jar, spindle, shaft connecting device, speed changer, electrical machine, frame, inner spiral ring band, temperature sensor, hot water sleeve interlayer, rotator flow meter, wet ball air flow meter, temperature controller and heat connecting pump, where the fermentation jar is installed horizontally on the frame, the bearing and bearing supporting seat is fixed on the frame, the spindle is inserted through the fermentation jar, one end of the spindle is connected with the bearing and the bearing supporting seat, while the other end is connected with the shaft connecting device, the shaft connecting device is connected with the speed changer, the speed changer is connected with the electrical machine, the top of the fermentation jar is provided with an air sampling pore, material feeding pore and hot water outlet, respectively, hot water outlet base is provided with a discharging pore, sludge sampling pore and hot water inlet, the external spiral ring band and the inner spiral ring band are coiled on the outside of the spindle, respectively, the temperature sensor is inserted into the fermentation jar, the temperature sensor is connected with the temperature controller, the temperature controller is connected with the wet ball air flow meter, the wet ball air flow meter is connected with the rotator flow meter, the rotator flow meter is connected with the air sampling pore, the hot water interlayer is covered on the outside of the temperature sensor and the joint between the spindle and the fermentation jar is provided with the seal set.