Electrochemical capacitors (ECs), also known as supercapacitors or ultracapacitors, have received considerable attention worldwide because of their potentially high-impact characteristics including high power capability, long cycle life, low maintenance and high reliability. From the perspective of fueling heavy electric vehicles, powering large industrial equipments, and storing intermittent renewable energy, currently, a major challenge in the field of ECs is to boost their energy density without sacrificing their power density and cycle life by exploring novel electrode systems with rational design of material composition, size, and morphology, as well as employing proper electrolytes. 2] Depending on the charge storage mechanism as well as the active materials used, ECs are generally classified into electric double-layer capacitors (EDLCs) and pseudocapacitors (or redox supercapacitors, PCs). The EDLCs, which usually use carbon-based active materials with high surface area as electrode, store charges electrostatically through reversible ion adsorption at the electrode-electrolyte interface, whereas the PCs utilize fast and reversible surface or near-surface redox reactions for charge storage, just like some metal oxides and conducting polymers. Polypyrrole (PPy), one of the most important conducting polymers, has been realized as a promising material for supercapacitors because of the charge storage in the entire mass of the conducting polymers and a high charge-discharge rate. However, pure PPy is usually mechanically weak and insulating in its neutral state. Therefore, various composites of PPy with metal, metal oxide nanoparticles, carbon nanotubes or graphene have been prepared to improve its mechanical, electrical, or electrochemical properties. Aligned carbon nanotubes (ACNTs) have been found to possess relatively high effective surface areas and low equivalent series resistance. The regular pores between ACNTs facilitate the fast transport of electrolyte ions in electrochemical energy storage process. It has also been proved that it is essential for reducing the contact resistance between the electrode material and the current collector in order to increase power density of the energy storage devices. ACNTs grown on the metal supports serve as the current collector, which could reduce the contact resistance. Thus, constructing PPy/ACNTs composite electrode materials would achieve a high specific energy and specific power as well as a good cycling stability. Herein, we report the preparation of PPy/ACNTs Composite materials by one-step electrochemical method. Compared with pure PPy, the as-prepared PPy/ACNTs electrode materials exhibit superior electrochemical performances including ultrahigh specific capacitances at different current densities and excellent cycling stability when investigated in three-electrode electrochemical cells (See Fig 1 to Fig 3 below). The strategy opens up a new window for developing further high performance conducting polymer based electrode for bridging the performance gap between traditional capacitors and batteries.