NOVELTY - Urban sludge anaerobic fermentation method to generate methane gas, involves (a) adding municipal sludge, high organic matter wastewater or livestock manure sludge in anaerobic reactor, detecting water content of the sludge, centrifuging the sludge, and storing the obtained product, (b) adding matrix pre-processing agent, (c) starting anaerobic fermentation reactor, and (d) calculating effective microbial biomass of each day in the reactor, and starting a fermentation system every day in a feeding ratio.    USE - Urban sludge anaerobic fermentation method to generate methane gas.    ADVANTAGE - The method is rapid and environmentally-friendly, produces no volatile fatty acid, and has excellent stability.    DETAILED DESCRIPTION - Urban sludge anaerobic fermentation method to generate methane gas, involves (a) adding municipal sludge, high organic matter wastewater or livestock manure sludge in anaerobic reactor, detecting water content of the sludge, centrifuging the sludge, where the water content is reduced to 85-90%, and storing the obtained product at 4 degrees C, (b) adding matrix pre-processing agent to the obtained sludge, controlling the water content to 78-80%, and storing the obtained product at 4 degrees C, (c) starting anaerobic fermentation reactor containing blending motor intermittent operation, and adjusting the stirring speed of the motor to 120 revolutions per minute (rpm), where the stirring time is 8-16 hours every day, the temperature control device of anaerobic reactor comprises water bath, and the temperature is maintained at 35 plus minus 1 degrees C, (d) calculating effective microbial biomass of each day in the reactor, and starting a fermentation system every day in a feeding ratio, where the feeding ratio of matrix to the effective microbial biomass is 10%, where the methane content is 50% or more. The methane content is calculated using specific equation involving predetermined parameters such as AB, F, n, alpha i, a1, a2, a3, a4, a5, a6 and a7, where AB is active biological quantity of sludge, F feeding quantity/day, n is number of days, i is day percentage, a1 is 25%, a2 is 20%, a3, a4 is 20%, a5 and a6 is 10%, and a7 is 5%.