The simultaneous reduction of the graphene oxide/polyaniline (GO/PANI) flake composites prepared by coating polyaniline (PANI) onto graphene oxide (GO) sheets was developed to prepare the novel electrode materials for the high performance supercapacitors. Firstly, the GO/PANI composites were prepared by the chemical oxidation polymerization of aniline in the aqueous dispersion of GO. Secondly, the reduced graphene oxide/polyaniline (R(GO/PANI)) flake composites were obtained by the chemical reduction of the GO/PANI composites with hydrazine hydrate as the reducing agent. Transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cyclic voltommetry (CV) were employed to investigate the morphology, thermal property, and electrochemical activity of the samples. TEM results revealed that PANI was polymerized on the surface of GO sheets and there was still thin PANI coating on RGO sheets after being reduced. The results of TGA and CV indicated that both the thermal stability and the electroactivity of the R(GO/PANI) flake composites were distinctly enhanced than those of the GO/PANI composites. In the R(GO-PANI) flakes, RGO played the dual roles: as electron acceptor and also as a counterion to stabilize an atypical intermediate oxidation state of PANI, which resulted in the high electroactivity of the R(GO/PANI) flakes.