Pseudocapacitive materials are known to suffer from severe capacitance loss during charging/discharging cycling. Here we report flexible all-solid-state supercapacitors (ASSSCs) based on reduced graphene oxide (rGO)/polypyrrole nanotube (PPy NT) papers prepared by a facile vacuum filtration method. It is revealed that the incorporation of rGO nanosheets can improve the electrochemical stability of PPy NT paper electrodes for pseudocapacitors. The hybrid paper electrode shows a high areal specific capacitance of 807 mF/cm2 at 1 mA/cm2 and a large volumetric specific capacitance of 94.3 F/cm3 at 0.1 A/cm3. The assembled ASSSC possesses a maximum areal specific capacitance of 512 mF/cm2 at 1 mA/cm2 and a maximum volumetric specific capacitance of 59.9 F/cm3 at 0.1 A/cm3. Moreover, it also exhibits excellent rate capability (86.3% capacitance retention from 1 to 10 mA/cm2) and cycling stability, little capacitance deviation under different bending states, a small leakage current and a low self-discharge characteristic. The device can provide an areal energy density of 61.4 μWh/cm2 at 10 mW/cm2 and a volumetric energy density of 7.18 mWh/cm3 at 1.17 W/cm3, indicating this high-performance ASSSC is a promising candidate for flexible high-power supply devices.