A polyaniline (PANI) film was electrochemically polymerized onto an ITO substrate by the pulse galvanostatic method in a reverse micelle electrolyte. The morphology of the as-prepared PANI was investigated by using a scanning electron microscope. An interesting result was that a nano-PANI was observed with a diameter of 100 nm. Further work involves investigating the potential application of the PANI films to a high performance supercapacitor electrode material. The energy density of the PANI was measured in HClO₄ solution. The highest energy density of nano-PANI arrays was 116.6 W h kg⁻¹ and kept as high 64.1 W h kg⁻¹ at a large charge–discharge current density (10 A g⁻¹). The cycle stability based on the PANI film electrode was investigated. The result showed that it had a low fading rate of its energy density after 500 cycles.