The graphene oxide/polyaniline (GO/PANI) composite was prepared by the one-step electrochemical co-deposition method. The different mass concentrations of GO were utilized to improve the electrochemical performances. Scanning electron microscope and transmission electron microscope images showed that PANI nanofibers not only were coated on the surface but also intercalated into GO sheets. The maximum specific capacitance of the GO/PANI composite achieved 1136.4Fg−1 with a GO concentration of 10mgL−1 at a scan rate of 1mVs−1, which is almost two-fold higher than that of PANI (484.5Fg−1). The GO/PANI composite also showed a good cycling stability, retaining over 89% of its initial capacitance after 1000 cycles. High electrochemical performances were attributed to increasing active sites for the deposition of PANI provided by large surface areas of GO sheets and the synergistic effect between GO and PANI, shortening the ion diffusion paths. Results indicate that the GO/PANI composites can be developed as excellent electrode materials of high-performance supercapacitor by a versatile, effective and environment-friendly method.