The application of biofiltration as final process to slightly-polluted water treatment is an economical and effective way to achieve organic pollutant removal and turbidity removal within the same filter unit. Further study has been conducted to evaluate the performance of biofiltration in removing organisms, NH4+ - N and turbiditythrough pilot-plant experiments. Results show that biofiltration can remove the organic matters as well as NH4+ - N effectively, and the effluent turbidity of biofiltration can maintain as low as that of traditional filtration.