Abstract: Multi-walled carbon nanotubes (MWNTs) were used as a conducting additive in activated carbon electrode materials instead of the commonly used carbon black and graphite powder conducting additive. It was found that MWNTs can greatly improve the capacitor performance. When 5 w/% MWNT conducting additive was used, the specific capacitance of activated carbon can be increased to 185 F/g compared with 130 F/g of activated carbon with 5 w/% carbon black conducting additive, and the frequency response characteristic of the MWNT added activated carbon electrochemical capacitor is much better than that of one with added carbon black. Moreover, some prototype electrochemical capacitors were fabricated on the basis of the research results. All these show that activated carbon with added MWNTs has a good capacitance performance and is suitable for application in electrochemical capacitors.