Abstract: A bacterium strain HS-03 was isolated from the activated sludge plant in a suburbof Wuhan city, China which has been found to be capable of aerobic denitrification. The effect of different inoculated amounts of pre -culturedmedia was analyzed. The denitrifying rates of this strain under aerobic and micro-anaerobic conditions were compared. The result indicated that the rate was almost not affected by the presence of oxygen.10m M nitrate was removed more than 90% in 36 hours by this bacterium in the specific medium. During the denitrifying process, nitrite was always kept at very low level.The denitrification potential of this bacterium was evaluated to treat artificialwastewater under fully aerobic conditions. Mainbiochemical and physiological featuresof this strain were characterized.The 16S rDNA sequence was comparedwith the published data inGenBank by using BLAST. The BLAST level of similarity to Pseudomonas stutzeri was 99. 1%. These results of phenotype and genotype proved that the strainHS03 was a new strain belonging to the species of P.stutzeri.