Nitrogen and boron co-doped activated carbon (BKACS) was synthesized through the carbonization, KOH activation and subsequently hydrothermal doping reaction process with chitosan as the renewable carbon source. The prepared samples were characterized by XRD, SEM, Raman, XPS and BET for their structure, morphology, specific surface area and elemental composition, respectively. The obtained BKACS has a specific surface area of 1129.6 m(2) g(-1), with high conductivity and capacitive character. The BKACS was applied as the electrode material to fabricate the electrochemical double-layer supercapacitor. The supercapacitor performed a high specific capacitance of 316 F g(-1) at 0.2 A g(-1) in a three-electrode system in the 6 M KOH electrolyte and excellent cycling stability with a capacitance retention of 94.08% after 10,000 cycles at 10 A g(-1). The attractive supercapacitor performance of the BKACS material has the high power density, excellent cycling life, and environmental friendliness, making it potentially a promising replaceable function for future energy storing device.