In this study, we report a facile strategy to prepare polyaniline and graphene nanopieces (PANI@GNP) nanocomposite by the oxidative polymerization of the aniline pre-assembled on the GNP surface. The morphology, chemical structure and interfacial interaction of the synthesized samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and x-ray photoelectron spectroscopy (XPS). The resulting PANI@GNP nanocomposite with a 0.33:1 mass ratio of PANI to GNP, has a large specific surface area, electron doping interface, excellent conductivity and reversible redox activity. The PANI@GNP symmetrical supercapacitor with the unique π-π electronic interaction demonstrates 351.7 F/g of specific capacitance; 57.5% of the rate property when the the current density increases from 1 to 10 A/g; the capacity retained 80% of the initial value in constant current charge–discharge mode (at the current density of 10 A/g) after 2000 cycles. This scalable preparation process makes PANI@GNP nanocomposite promising application in electrochemical devices. [ABSTRACT FROM AUTHOR]