Abstract: A method for realizing heterotrophic and autotrophic coupling advanced nitrogen removal and simultaneous sludge reduction in an anaerobic-aerobic-anoxic sequencing batch reactor (AOA-SBR) is disclosed. Municipal sewage and sludge fermentation mixture is allowed to simultaneously enter into the AOA-SBR; in the anaerobic stage, the organic matter in the sewage and sludge fermentation mixture is converted into polyhydroxyalkanoates (PHA) and stored in the body; in the aerobic stage, the dissolved oxygen (DO) at 0.5˜1 mg/L is maintained by a real-time control, the aeration time is set for 1˜3 h, and when the mass concentration ratio of NO2?—N to NH4+—N is in a range from 1.5 to 2.