Hierarchical porous activated carbon (AC) was obtained from corn stalk pith with a hierarchical macroporous nature, which is composed of cells of soft and spongy texture. The high specific surface area (2495m2 g−1) of the activated carbon (AC) was produced by the activation of corn stalk core (CSC) using potassium hydroxide at 700°C. SEM, TEM and XRD were used to test the microstructure and crystallographic orientation of the carbon samples. The cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy were measured based on CSC-700. This sample had relatively low inner resistance of 1.0Ω. The specific capacitance was 323Fg−1 in 6molL−1 KOH electrolyte at a current density of 0.1Ag−1, and it still maintained very good cyclic stability with capacitance retention ratio of 97.9% (from 265.0 to 262.4Fg−1) at current density of 1.0Ag−1 for 1000 cycles.