A series of N/O co-doping porous carbon materials are fabricated from benzotriazole as nitrogen-containing precursor through simple chemical activation (phosphoric acid as activator) and thermolysis process under nitrogen atmosphere. Abundant heteroatoms or functional groups (O: 11.4at.%; N: 6.5at.%) in the N/O-3-700 sample can improve the overall electrochemical performance of the material, which is because they can enhance physicochemical properties and induce the pronounced pseudocapacitance. In three-electrode system, the resultant product (N/O-3-700) has a highest specific capacitance value of 357.8Fg(-1) at 0.1Ag(-1) and good cycle stability (remains more than 94% after 10000 at 1Ag(-1)), which are attributed to large specific area (1337.7m(2)g(-1)) and proper functional groups (the sum of N-5 and N-6 content: 42.2at.%; quinone: 14.3at.%, C=O and/or COOH: 16.0at.%). And in symmetric two-electrode cell, the N/O-3-700//N/O-3-700 cell possesses highest energy density of 17.80Whkg(-1) at 1Ag(-1) and still has a high energy density (12.51Whkg(-1)) at 10Ag(-1). Thus, the N/O-doped porous carbon can be used for supercapacitors.