A strain of bacteria CP1 with high nitrogen removal efficiency was newly isolated from the biofilm of a biofilter for removal of NO x from flue gas. The isolate was identified as Pseudomonas aeruginosa based on its physiological and biochemical characteristics and the results of 16S rRNA gene homology analysis. The new isolate had a high denitrifying ability, removing 98.49% of the nitrate in a 24-h period under aerobic conditions, with no nitrite accumulation. With regard to the nitrogen balance, the percentage of nitrogen lost in the flask culture was estimated to be 32.3%, which was presumed to be converted to nitrogen gas. An analysis of its denitrification activity showed that the optimal C/N and temperature were 12 and 30°C-40°C, respectively. By using glucose, sodium citrate and succinate, CP1 removed nitrate with high denitrification efficiency. The change in DO did not influence the effects of denitrification when it varied from 0 to 7.2 mg/L. The results show that CP1 could be a good candidate for the process of aerobic denitrification.