Abstract: Polyaniline was electrosynthesized on a carbon fiber electrode in sulfuric acid by the cyclic voltammetric technique. The voltammogram showed four reversible redox systems with the growth process. The electrodeposition charge on the carbon fiber electrode corresponding to the growth of polyaniline increased with increasing aniline and electrolyte concentration, and increased with decreasing scan rate. The open structure morphology of polyaniline was observed by scanning electron microscopy. According to theoretical calculation and the morphology of polyaniline it was proposed that the electrochemically synthesized polyaniline consisted of two types of layers. The first one formed at the early stage of growth and was of a compact structure, while the second layer was of a less dense open structure.