The biocathode of the two-columnar microbial fuel cell was used to denitrify. Factors influencing denitrification performance and power production were studied. When the external resistance decreased from 50 omega to 5 omega, the nitrate removal rate increased from 0.26 mg/(L x h) to 0.76 mg/(L x h). The nitrite accumulated to 55 mg/L with the external resistance decreasing to 5 omega. The nitrate degradation followed the zero order reaction model when the initial nitrate concentration was 20-120 mg/L. The power generation was not affected by the nitrate concentration distinctly. The nitrite concentration increased with the initial nitrate concentration. The nitrite removal could be enhanced by adding organic matter, without significant influence on the power generation.