NOVELTY - Algae anaerobic digestion for producing marsh gas, involves: (1) putting algae residue (12-26 g), then adding cellulose to obtain the reaction solution; (2) concentrating by adjusting the pH value, adding neutral protease, stirring them uniformly in 40 degrees C revolution per minute (rpm) oscillating reaction for 3 hours to obtain the enzymolysis product of neutral protease; and (3) adding anaerobic digested sludge, and then adding the obtained enzymolysis product, adding water (0.8 liter), stirring, introducing nitrogen blowing the residual air in bottle, obtaining methane-containing biogas.    USE - As algae anaerobic digestion for producing marsh gas, particularly methane-containing biogas (claimed).    ADVANTAGE - The process solves the problem that includes the substrate is hydrolyzed into the problem of speed limit step of the whole anaerobic digestion process, and there is no waste generated, post-processing can be directly used for anaerobic digestion. The process improves yield of methane i.e. 29.9-57.7% on the average ratio in the gas.    DETAILED DESCRIPTION - Algae anaerobic digestion for producing marsh gas, involves: (1) putting algae residue (12-26 g) 1:5 (wt./wt.%), adding pH value of 4.8, the concentration is citric acid buffer solution of 50 mmol/L, then adding cellulose in shaking table of 50 oscillating reaction for 48 hours to obtain the reaction solution, where the cellulose is acremoniumcellulase activity unit is 400 filter paper enzyme activity/g; (2) concentration by adjusting the pH value of the reaction liquid is NaOH solution with the concentration of 1 mol/l for 7, adding neutral protease, stirring them uniformly in the 40 degrees C revolution per minute (rpm) oscillating reaction for 3 hours to obtain the enzymolysis product of neutral protease activity is 60000 activity units/g, temperature is 40 degrees C and the pH value is 7-7.8; and (3) adding anaerobic digested sludge is wide opening with a plug bottle as main body, and then adding step the obtained enzymolysis product, adding water to 0.8 L, stirring them uniformly, the upper part cover is provided with guide tube of the bottle filling, introducing nitrogen blowing the residual air in the bottle, outlet is connected with air bag for collecting the gas jar are put into 35 degrees C of water bath to anaerobic digestion to obtain methane-containing biogas.