MnO2 was doped into a conducting copolymer, poly(aniline-co-o-aminophenol)(PANOA), via a one-step process during the chemical oxidative polymerization. The doping of MnO2 could enhance the electrochemical activity and reversibility of the copolymer. When used as the electrode materials of a supercapacitor, the capacitive behaviors of the as-prepared PANOA–MnO2 were superior to those of pure PANOA, especially at high potential scan rate and high charge–discharge current density. The MnO2 doped copolymer also had an excellent cyclic performance. The doping of MnO2 could enhance the electrochemical activity and reversibility of the copolymer. When doping of MnO2 could enhance the electrochemical activity and reversibility of the copolymer. When MnO2 was doped into a conducting copolymer, poly (aniline-co-o-aminophenol) used as the electrode materials of a supercapacitor, the capacitive behaviors of the as-prepared PANOA-MnO2 were superior to those of pure PANOA, especially at high potential scan rate and high charge-discharge current density. The MnO2 doped copolymer also had an excellent cyclic performance.