Nanostructured composite web were prepared with multi-walled carbon nanotube (MWCNT) in polyacrylonitrile (PAN) by electrospinning technology. The diameters of the fibers showed narrow distribution to be averaged of 300 nm. The alignment of MWCNT along the fiber direction has been successfully achieved. The MWCNT/PAN composite fiber web was oxidatively stabilized in air and followed by steam activation, resulting in activated carbon nanocomposite fibers (ACNCFs). 1 wt.% addition of MWCNT increased the specific capacitance by two times more from 82 to 160 F/g. The enhancement of the capacitance was well explained by the increase in the specific surface area and the reduced resistance by the addition of MWCNT.