The invention discloses an optimizing method of enriched ammonia-oxidizing bacteria in an activated sludge population structure, belongs to the technical field of enhanced biological sewage denitrification processing, aims at solving the practical problems of trenchant running condition requirements, long cultivation time of enriched ammonia-oxidizing bacteria and high running energy consumption in current denitrifying techniques with short-course nitration and denitrification, and develops the optimizing method of enriched ammonia-oxidizing bacteria of the activated sludge population structure according to the growth characteristics of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in an activated sludge processing system. The optimizing method of enriched ammonia-oxidizing bacteria of the activated sludge population structure is mainly characterized in that a nitration reaction process is controlled with parameters of pH value and DO, aeration is halted before ammonia peak valley appears, ammonia-oxidizing bacteria is completely proliferated, proliferation chance of NOB is deprived, and nitrite-oxidizing bacteria is eliminated from the system by controlling sludge age, thus achieving the goal for the quick start of short-course nitration and denitrification. A bisection method is utilized in the operating process so as to determine the optimal time for advancing aeration halt. Furthermore, the optimizing method of enriched ammonia-oxidizing bacteria of the activated sludge population structure has the advantages of short reaction period, high enrichment efficiency, simple operation and the like.