To increase the performance of MFCs, nitrogen-doped activated carbon (AC) for rolling-pressed air-cathode was synthesized using inexpensive melamine as nitrogen source by pyrolysis. The ratio of melamine to activated carbon (N/C) and pyrolysis temperature were optimized to be 10 and 900 degrees C. To clarify how the structure and active nitrogen content in different preparations influence the ORR performance, series of characterizations were carried out, and a good agreement between the content of pyridinic type N and high ORR activity was observed. As a dominant four electron cathode catalyst, AC-N10-900 exhibited the best performance both in electrochemical and MFCs tests in comparison with AC and Pt/C. The maximum power density was 1042 m W m(-2), which was 65.4% and 116.2% higher than that of AC and Pt/C. Therefore, AC-N10-900, one of cost-effective and metal-free MFCs cathode catalysts towards ORR, is expected to alternate precious metal for high performance in MFCs.