An aerobic denitrifier Y4 is isolated from the activated sludge of UCT system’s aerobic reactor, which is identified as Gordonia.sp according to the 16S rDNA similarity comparison and analysis. The study on denitrification capability of strain Y4 shows that strain Y4 could effectively remove the nitrate nitrogen in the culture under aerobic conditions, and the nitrogen removal efficiency within 48 hours up to 61.2% when the initial concentration of nitrate nitrogen is 286 mg/L. Another test investigated the effects of denitrification on DO and temperature, the results show that strain Y4 has a high oxygen tolerance. When the DO is 2~11.8 mg/L, the denitrification rate could be maintained at a high level. Strain Y4 also has a high temperature adaptation, the denitrifying rates is up to 90% at 30 ℃. The tests prove that there is aerobic denitrifier which has good performance of aerobic denitrification in the SUFR-UCT system.