Composite films of graphene and polyaniline nanofibers are prepared by in situ polymerization of aniline monomer in graphene suspension. The morphology and microstructure of samples are examined by scanning electron microscopy (SEM), transition electron microscopy (TEM), and X-ray diffraction (XRD). Electrochemical performances are characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge measurements. Graphene is homogeneously coated by polyaniline nanofibers with diameter of 40 nm. Supercapacitors based on the graphene/polyaniline conductive composite films exhibit large electrochemical capacitance (994 F/g) at a discharge rate of 2.0 A/g in 1 M H2SO4 solution, which is much higher than the graphene (320 F/g) and polyaniline electrode (210 F/g). The excellent performance is not only due to the graphene which can provide more active sites for nucleation of polyaniline, but also associated with a good redox activity of ordered polyaniline nanofibers. Moreover, the composite films exhibit excellent long cycle life during charge/discharge processes. After 1000 cycles, the specific capacitance decreases 11% of initial capacitance compared to 28% for polyaniline nanofibers. The resulting composite is a promising electrode material for high-performance electrical energy storage devices.