Abstract: The phenolformaldehyde resin activated carbon without ‘ink bottle’ porous structure was first introduced to study the influence of porous structure on capacitance of electrode material. The relation between the porous structure of the activated carbon and its electric double-layer capacitance, and the effect of its pore size distribution on discharge rates were discussed by means of nitrogen gas adsorption, AC impedance spectroscopy and constant current discharge techniques. The capacitance of activated carbons is attributed to both external surface (pore diameter > 2.0 nm) and micropore surface (pore diameter < 2.0 nm), but mainly to the latter. The capacitance on the microporous surface is 21.4 μF•cm－2, on the external surface < 10 μF•cm－2. Possibly the space charge layer exists on the interface in series with electric double layer, which makes the capacitance on the external surface much smaller than the usual capacitance. The activated carbon with larger micropore has larger specific capacitance and higher discharge rate.