In recent years, electrochemical supercapacitors have aroused wide advantages due to strong demand for flexible, portable, and lightweight energy devices. Supercapacitors are promising power source for automotive applications, have many advantages compared to traditional capacitors and secondary batteries such as high power density, environmental safety, high rate capability, long durability, and long cycle life. Polyaniline (PANI) nanotubes have great potential electrical application in supercapacitor electrode material. For the preparation of conducting polymer nylon 6,6/polyaniline (PANI) core-shell nanofibers with high electrical conductivity, nylon 6,6/polyaniline (PANI) core-shell nanofibers composite webs were fabricated by in situ polymerization of aniline using the electrospun nylon 6,6 fiber as a template. Different aniline concentrations of 0.125, 0.25, and 0.5 M were used for polymerization, respectively. Thus, core-shell Nylon 6,6/PANI nanofibers with different diameters correspondingly marked as N66/PANI #1, #2, and #3 for increasing three aniline concentrations. The morphology of nylon 6,6/PANI core-shell nanotubes has been carefully analyzed by field emission scanning electron microscopy. The diameter of the pristine nylon 6,6 nanofibers is uniform with an average size about 200 nm. It can be observed that the diameters of N66/PANI #1, #2, and #3 core-shell fibers are about 292, 312, and 425 nm, respectively. In summary, nylon 6,6/PANI core-shell nanofibers have been successfully obtained by in situ polymerization of aniline using the electrospun nylon 6,6 nanofibers as a template. The N66/PANI core-shell nanofibers exhibited high specific capacitances with good cycling stability in 1.0 M H2SO4 aqueous solution. This finding promoted the development of advanced electrode materials, indicating huge potential for supercapacitors. Acknowledgement This work was supported by National Research Foundation of Korea (grant no.: 2013M2B2A4041305 and 2013R1A2A2A04013913). Keyword: Supercapacitors, Nylon 6,6, Polyaniline, Core-shell, Nanofibers, Electrospinning