Present work investigated the nitrogen dynamic and the evolution of ammonia oxidizers during aerobic treatment of three kinds of organic wastes including municipal solid wastes, mixture of municipal solid wastes and waste activated sludge, digested sludge. Experimental results suggest mineralization of organic nitrogen was correlated to biodegradability and ratio carbon / nitrogen of each type of waste. The mineralization of organic nitrogen following the intense biodegradation stage of organic wastes contributed to ammonia emissions. Although ammonia oxidation occurred in the early phase during treatment of the mixture and digested sludge, the oxidation flow was much lower than ammonia emissions. For each waste, an increase of ammonia oxidation occurred similarly at the end of treatment. Ammonia-oxidizing bacteria were more abundant than ammonia-oxidizing archaea. Only the evolution of ammoniaoxidizing bacteria was correlated to ammonia oxidation flow. These findings suggest only ammonia-oxidizing bacteria were responsible for ammonia oxidation during aerobic treatment of three kinds of organic wastes.