Two-dimensional plate-like PANI are successfully synthesized by a self-assembly process using benzoyl peroxide as oxidant. The micelles formed by aniline/p-TSA salt serves as ‘soft template’ to form PANI micro/nanostructures and proper [An]/[acid] ratios are required for the formation of plate-like PANI. It is found that at high [An]/[p-TSA] ratios (5:1 to 2:1) plate-like PANI are obtained, while at low [An]/[p-TSA] ratios ranging from 1:1 to 1:3 PANI nanoparticles are obtained. The influence of the other synthetic parameters, such as temperature, the concentration of benzoyl peroxide and stirring, on the morphologies of the PANI micro/nanostructures has also been investigated. Fourier transform infrared (FTIR), UV–vis spectroscopy (UV–vis), X-ray photoelectron spectroscopy (XPS), as well as X-ray diffraction (XRD) and cyclic voltammeter method (CV) are applied to characterize the products.