In this paper the phosphorus removal performance has been studied in Non-backflow Intermittent Aeration System (NBIAS), when the aeration duration and SRT were adjusted. At the same time, nitrogen removal was also studied. Test results show that when the cycle duration is 6 h., anaerobic duration 1.5h. sedimentation and displacement time 0.5 h. and SRT=20 d,aerobic ratio 0.42, the removal efficiency for CODcr, nitrogen and phosphorus will be 85%, 75% and 69%, respectively.