In this study, we report the fabrication of nitrogen rich activated nanosized carbon with hierarchical micro/mesoporous and ultrahigh specific surface area by template-free and one-step carbonization-activation method, which greatly simplified the process and avoided the waste of reagents. Chitin nanoparticles were prepared by a mechanical induced sol-gel transition process in NaOH/Urea solvent and a subsequent carbonization utilizing NaOH for activation and urea for N doping, resulting in activated carbon (ACNC-800) with extraordinary specific surface area (2631 m2/g) and high nitrogen content (7.1%). Further characterization and electrochemical tests demonstrate high electrochemical performance of the activated nanocarbon. Under the current density of 0.5 A/g, the specific capacitance of the three-electrode system is 245 F/g and that of the two-electrode system is 227 F/g. The assembled capacitors exhibit superior rate performance and good cycle stability (98% capacitance retention after 10000 charge-discharge cycles). This work introduces a simple and efficient strategy to prepare N-doped carbon with hierarchical porosity applied to high performance supercapacitors.