The synthesis of triple-layer-structured polyaniline (PANI) conductive nanocomposites, including two-dimensional leaf-shaped and three-dimensional flower-shaped types (S-PANI), via a two-step method is proposed in this study. According to scanning electron microscopic measurement, the triplelayer-structured S-PANI consists of a middle layer of nonconductive PANI (N-PANI) at 100 nm thickness and emeraldine-salt-form PANI (ES-PANI) nanolayer at 40-50 nm thickness. The results of Fourier-transform infrared spectroscopy, UV/Vis spectroscopy, and X-ray diffraction pattern demonstrate that the phenazine unit existed within the N-PANI main chain, leading to the poor conductivity of N-PANI. However, the conductivity of the N-PANI can be extremely enhanced by at least nine orders of magnitudes (<10 −9-10 0 S/cm) when a conductive ES-PANI nanolayer is further grown on the N-PANI outer surface. Finally, the results of oxygen transmission test and electrochemical impedance spectroscopy reveal that the leaf-shaped S-PANI, as an additive in epoxy resin, has the best oxygen barrier property (oxygen transmission rate = 5.86 cm 3 m −2 day −1) and highest coating resistance (5.53 × 10 10 Ω) after 60-day immersion in 0.1 M HCl solution, indicating that the leaf-shaped S-PANI is an excellent anticorrosion additive.