The nitrogen-removing characteristics of Pseudomonas stutzeri T13, a heterotrophic nitrifying-aerobic denitrifying bacterium, were investigated. The ammonium and nitrate removal of the bacterium was found to reach nearly 100 % at 15 h. However, the total nitrogen (TN) removal rate reached only about 23.47 % because of the dramatic accumulation of nitrite at a high dissolved oxygen (DO) level (160 rpm). The process of nitrite reduction was found to be the bottleneck for the efficiency of aerobic denitrification. Decreasing the shaking speed from 160 to 50 rpm to lower the DO concentration during cultivation was an effective method of improving nitrite utilization because nitrite removal increased from 62.37 to 100 %. The 99.21 % capability of simultaneous heterotrophic nitrification and aerobic denitrification with TN removal was achieved at a relatively low DO level (50 rpm).