The aim of this study was to screen aerobic denitrifying strain from various environmental sites and to investigate the denitrification conditions for the isolated strain. Enrichment culture technique was used in screening and acclimatization of strain, a rhizosphere aerobic denitrifying bacterium RWX31 was isolated and single-factor experiments were used to investigate the denitrification conditions and characteristics. The nitrate remove efficiency of aerobic denitrifying strain RWX31 was 82% when cultivated in 140 mg/L nitrate for 24 hours, N2O could be produced aerobically through aerobic denitrification of strain RWX31. The optimum medium was: sodium citrate as carbon source, 1% inoculation volume, 0.05 g/L Mg2+ concentration and nitrite proportion of 0 in the initial denitrification nitrogen source. The optimum condition was: temperature 28℃-32℃, pH 7.0-7.5, C/N ratio 8-12 and DO concentration 6.5-7.0 mg/L. The highest nitrate removal efficiency was higher than 90% under the above conditions. Rhizosphere bacterium RWX31 was an efficient aerobic denitrifying strain with higher nitrate removal efficiency than reported previously and has application potential.