The invention provides a methanation, denitrification and anammox coupling process based sewage treatment process. The process is characterized by comprising the following steps: (1) inoculating granular sludge with denitrifying dephosphatation function in an air-lift anaerobic reactor to ensure that the sludge concentration in the reactor is between 5 and 10g/L; (2) pumping the sewage to be treated into the air-lift anaerobic reactor, wherein the sewage to be treated at least contains HCO3-, CO2, NH4+, SO42-, NO3- and PO43-; (3) carrying out air-lift stirring on the pumped sewage by using aninternal circulating gas pump, depositing the sewage after the sewage performs an anaerobic reaction for 3 to 5 hours under an anaerobic condition that the temperature is of 32+/-1 DEG C; (4) discharging supernate out of the system after deposition; and (5) discharging 10 to 40 volume parts of sludge when the sludge volume is more than 30 percent of the reactor volume. The process realizes coupling of methanation, denitrification and anammox, and simultaneously realizes removal of COD, ammonia nitrogen and total nitrogen in the air-lift anaerobic reactor.