Various kinds of activated carbon materials were investigated by means of nitrogen gas adsorption, AC impedance and constant current discharge techniques. The relation between the intrinsic pore size distribution of activated carbon materials and their electrochemical performance as electrodes of supercapacitor were discussed in detail. Activated carbons with larger pores are found to be more suitable for high power applications. The electrochemical accessible time to pores of various sizes obtained from the fitting of AC impedance data was successfully correlated with the pore size distribution of the materials.