In this work, cotton stalks (CSs), as an earth-abundant biomass, were originally proposed as a new carbonaceous precursor to prepare hierarchically porous carbons (HPCs) with the activation of various concentrations of H3PO4 at high temperatures. A variety of measurements including SEM, TEM, N-2 adsorption/desorption analysis, XPS and FTIR have been adopted to systemically investigate the micromorphology, pore structure, and surface chemistry of the HPCs. The CS-derived HPCs (CSHPCs) have large specific surface areas up to 1403.123m(2)g(-1) and a broad pore-size distribution indicates their hierarchically porous structures. Furthermore, electrochemical measurements including electrochemical impedance spectroscopy, galvanostatic charge/discharge and cyclic voltammetry were used to evaluate the capacitance and rate performance of the HPCs. The investigations illustrated that CSHPCs possess a high specific capacitance up to 175Fg(-1) at a scan rate of 5mVs(-1) in 2M KOH. In addition, CSHPCs have good long-term cycling stability and more than 90% of the initial capacity is retained after 10000 cycles at a large current density of 1Ag(-1).