In order to solve the contradictions in three aspects existing in the traditional AAO method, that was the sludge ages, the demand for carbon source and the phosphorus release of phosphorus accumulating organisms (PAOs) in the anaerobic process influenced by the nitrates carried in the inverse sludge in three kinds of bacteria (i.e., nitrifying bacteria, denitrifying bacteria and PAOs), to reduce a large amount of reflux sludge, to lower power consumption, to make full use of tank capacity, and to improve the efficiency of sewage treatment practically, the concept of "three sludge" was put forward and the key improvement of AAO was carried out. The improved biochemical reaction tanks such as anoxic tank, anaerobic tank and aerobic tank were equipped with independent automatic separation devices of mud and water to form a unique three sludge system, which were pure anaerobic sludge, pure anoxic sludge and pure aerobic sludge. Each tank was able to control the sludge concentration according to the operation requirements, so that the activated sludge in each tank grew independently in their optimal environment without mutual interference in order to achieve a more efficient biodegradation. The coupling process of the improved AAO +biofilter +flocculation was innovatively designed to treat antibiotic pharmaceutical wastewater and was compared with the traditional combination technology. The results showed that the improved technology had a good treatment effect under the conditions of CODcr 253~581 mg/L, ammonia nitrogen 29.6~58.5 mg/L, total phosphorus 10.77~23.1 mg/L, design flow rate 30.0 L/h in influent. The average removal rates of CODcr, ammonia nitrogen and total phosphorus were 80.2%, 73.1% and 96.1%, respectively, which were 6.9%, 6.1% and 3.4% higher than those before improvement, respectively. All three indexes of CODcr, ammonia nitrogen and total phosphorus in tail water were in accord with the first great standard of the Integrated Sewage Discharge Standards (GB8978-1996).