Nitrogen-doped nanoporous carbon materials with large BET surface area (1322.5m2 g−1) and pore volume (0.87cm3 g−1) have been achieved by a synchronous carbonization/nitridation process, simply using potassium biphthalate and azodicarbonamide as carbon/nitrogen sources, respectively. The above carbon materials have been further impregnated with MnOx nanocrystallites that comes from the thermal decomposition of Mn(NO3)2. Taking the carbon-2:1-Mn sample as an excellent example, it also has large BET surface area (1160.1m2 g−1) and pore volume (0.77cm3 g−1) and exhibits high nitrogen/manganese contents of 4.13%, and 3.30%, respectively. The carbon-2:1-Mn sample delivers excellent capacitances of 564.5 and 496.8Fg−1 at the current density of 0.5 and 1.0Ag−1, respectively, as well as superior cycling stability of 96.10% even after charging/discharging for 5000 times. The present method of incorporating cheap MnOx substance into carbon matrix is efficient and also easy for large scale production of carbon nanocomposites, especially possessing large BET surface area and high pore volume.