In order to study the effect of replacing old and new processes in denitrifying deep-bed filter, the water quality data before and after equipment upgrading at the same period were collected for comparative analysis. The results show that the new process has a desirable removal rates for COD (93.67%), BOD (96.82%), NH₃-N (98.04%) and SS (97.47%) throughout the year, respectively, with the effective and feasible denitrification process. The average TN concentration in effluent was 6.1mg/L after process upgrading, which decreased by 41.69% compared with the same period before process upgrading. The average removal rate was 72.5%, which was much higher than that before replacement (58.8%). In general, the denitrification deep bed filter had a great nitrogen removal efficiency.