Porous activated carbons (AC) have been synthesized from natural biomass material amorphophallus konjac powder by one-step method to make a carbonization and activation with potassium hydroxide. The three-electrode system tests show that the porous structure KGAC-X samples have excellent electrochemical performance, especially the KGAC-2 electrode showing superior specific capacitance (169.8 F g(-1), current density 1 A g(-1)) and excellent rate performance (212.5 F g(-1), current density 1 A g(-1)) in the 1 M KOH electrolyte. This study provides a facile, economical, and effective route to prepare commercial activated carbon electrode material with high porosity for supercapacitors. (C) 2019 The Electrochemical Society.