The　kinetics　of　oxygen　reduction　of　cathode　catalyst　is　a　critical　factor　that　limits　the　performance　of　microbial　fuel　cells　(MFCs).　The　composite　catalyst　of　three　composite　proportion　(1:3,　1:1　and　3:1),　which　were　prepared　by　reacting　KMnO4　with　supercapacitor　activated　carbon　(S-AC),　were　tested　as　air-cathode　catalyst　of　microbial　fuel　cells　(MFCs)　for　oxygen　reduction.　X-ray　diffraction　(XRD)　was　used　to　characterize　the　catalysts,　energy　dispersive　X-Ray　Spectroscopy　to　estimate　the　quality　of　MnO2,　scanning　electron　microscopy　(SEM)　to　observe　the　surface　morphology,　and　BET　method　to　examine　surface　area　and　pore　distribution　characteristics,　to　analyze　the　factors　affecting　the　performance　of　the　composite　catalyst.　With　increasing　of　composite　proportion,　the　MnO2　sheets　gathered　into　nano-particles　(300-500　nm)　on　the　surface　of　S-AC.　At　the　same　time,　there　is　the　decrease　of　the　internal　and　external　surface　area　MnO2/S-AC.　Nickel　foam　air-cathode　was　made　with　different　catalysts,　and　tested　in　air-cathode　MFCs　to　study　the　effect　on　MFC　performance　by　linear　sweep　voltammetry　(LSV),　polarization　curves　and　power　density　curve.　When　the　feeding　ratio　of　KMnO4:　S-AC　is　1:3,　the　maximum　power　density　was　321.2　mWm-2,　which　was　increased　by　about　20%　over　the　S-AC　loading　MFC.　However,　when　the　feeding　ratio　was　increased　to　1:1　and　3:1,　the　maximum　power　density　decreased　to　240.9　and　160.3　mWm-2.　MnO2/S-AC　composite　catalyst　within　a　certain　ratio　range　could　effectively　improve　the　performance　of　air-cathode　and　MFC,　which　helps　to　the　expansion　application　of　air-cathode　MFC.　©,　2015,　Chemical　Industry　Press.　All　right　reserved.