A total of 8 pure strains of ammonia-oxidizing bacteria (AOB) were collected from the rhizosphere of wetland plants including Arundo donax, Herb of rice galingale and willow. By microscopic observation and color reaction of Griess reagent, two strains of YL-1 and YS-2 were selected as the dominant genus to conduct performance investigation. Bath experiment results demonstrated that YL-1 shows the similar properties with YS-2 on the degradation of ammonia under the conditions of different pH value, ammonia loading and oxygen concentration. Both the two strains all showed excellent adaptability to the conditions of strong alkaline (pH=8.5) and high free ammonia (FA) concentration (18.2 mg/L). In spite of it, the ammonia degradation performance of the two strains to the high ammonia loading was all inhibited by the low DO condition.