NOVELTY - Producing methane by excess sludge using microbial electrolytic cell comprises taking excess sludge as a substrate for domesticating anodic functional microorganism and starting an electrolytic cell reactor, taking a direct-current power supply as a power supply for applying voltage of 0.4-0.8 V at the two ends of the electrolytic cell, mixing the excess sludge with a nutrient solution A to obtain a mixed solution with a concentration of 9-24 g/l, and adding water into the electrolytic cell in a closed loop.    USE - The method is useful for producing methane by excess sludge by microbial electrolytic cell (claimed).    ADVANTAGE - The method rapidly and economically produces the methane with high productivity in an eco-friendly manner.    DETAILED DESCRIPTION - Producing methane by excess sludge using microbial electrolytic cell comprises taking excess sludge as a substrate for domesticating anodic functional microorganism and starting an electrolytic cell reactor, taking a direct-current power supply as a power supply for applying voltage of 0.4-0.8 V at the two ends of the electrolytic cell, mixing the excess sludge with a nutrient solution A to obtain a mixed solution with a concentration of 9-24 g/l and then adding water into the electrolytic cell in a closed loop under the condition that the voltage at the two ends of the resistor is lower than half of the initial voltage, continuously replacing the mixed solution B for domesticating and enriching the anodic functional microorganism until the resistance voltage is continuous stable for starting the microbial electrolytic cell reactor, taking excess sludge as the substrate, taking the direct current power supply as the power supply for applying voltage of 0.4-0.8 V at the two ends of the electrolytic cell, adding the alkali into the excess sludge for pre-treating to obtain a mixed solution C, dissolving the mixed solution C in the nutrient solution A for obtaining a mixed solution D with the concentration of 9-24 g/l and then adding into the electrolytic cell in the closed loop under the condition that the voltage at the two ends of the resistor is lower than half of the initial voltage, replacing a novel mixed solution D and then reacting at 26-30 degrees C for 2-6 days for finishing product, where the: excess sludge is a secondary settling pond of the urban domestic sewage treatment plate; anode of the microbial electrolytic cell reactor is carbon fiber; cathode is non-immersed carbon cloth and coated with platinum catalyst; and cathode is present in an anaerobic state during the electrolysis. The nutrient solution A comprises disodium phosphate (11.6 g), monosodium phosphate (2.8 g), ammonium chloride (0.3 g), potassium chloride (0.1 g) and extra distilled water. The alkali is sodium hydroxide of 4 mol/l. The voltage is measured by keithley 2700 data acquisition system.