Abstract: To investigated the effect of biological aerated filter on corn silage effluent, four main influencing factors (hydraulic loading, gas-water, organic loading and filter bed height) on BAF system were studied in this experiment. The results showed that the removal rate of COD and NH3-N were increased at first and then decreased under 0.5 m3/(m2·h) to 3.0 m3/(m2·h) of hydraulic loading; with 1.5 m3/(m2·h) of hydraulic loading, the maximum of the removal rate of COD and NH3-N obtained were 83.5%, 74.9%, respectively. The removal rate of COD and NH3-N were increased with the increasing of the gas-water ratio at the gas-water ratio of 3.5:1; the removal rate of COD and NH3-N reached the highest, at 87.5% and 75.2%, respectively. The removal rate of COD and NH3-N was 49.6% and 58.5% with 2.4 kg/(m3·d) of the organic loading COD, respectively, reached the maximum(80.9% and 75.9%, respectively) with 4.8 kg/(m3·d) of the organic loading COD, and was low with 7.2 kg/(m3·d) high organic loading, about 61.7%. The influences of filter bed height upon NH3-N removal were extremely significant, the removal rate of NH3-N at the height range 0.6 to 1.0 m was higher than the others. Therefore, it is feasible and effective to treat corn silage effluent by BAF system. The results provide useful references for wastewater treatment and rural water environmental quality control.