The activated carbon with honeycomb-like morphology for electrochemical double layer capacitors (EDLCs) was prepared from wheat straw by carbonization and subsequent activation with KOH. The product presented micro- and mesoporous structure with the peak pore size of 2.1nm and high specific surface area of 2316m 2 /g. The electrochemical capacitance performances of the activated carbon as EDLC electrodes were characterized by using cyclic voltammetry (CV), alternating current (AC) impedance. The specific capacitance of the activated carbon reached 251.1F/g at 2mV/s scan rate in the electrolyte of MeEt 3 NBF 4 /AN. The thermal gravimetric analysis of AN impregnated carbon was explored as a new approach to investigate the effectivity of pore for the electrolytes. The relationships between specific capacitance and scan rate, surface area and pore diameter were discussed.