Flexible all-solid-state supercapacitors with specific energy higher than 1 mW h cm(-3) after long-term cycles remain a hot research topic in energy storage systems. In this paper, free-standing reduced graphene oxide/polypyrrole films are produced at the ice/ethanol interface following by hydrogen iodide reduction. The reduced graphene oxide/polypyrrole films are featured with high specific surface area, three-dimensional porosity, and tunable thickness and electronic conductivity. The typical flexible all-solid-state supercapacitor based on reduced graphene oxide/polypyrrole films exhibits a high volumetric specific capacitance of 17.3 F cm(-3) and a high specific energy of 2.40 mW h cm(-3) with corresponding specific power of 136.1 mW cm(-3) at a current density of 3 mA cm(-2) (ca. 10 Ag-1 After 10,000 cycles at 3 mA cm(-2), the capacitance retention of the typical flexible supercapacitor retains 73.2%. The enhanced electrochemical properties of the flexible supercapacitors are attributed to the high specific surface area, three-dimensional porosity, and the synergistic effect between reduced graphene oxide and polypyrrole with respect to the composite films.