For practical applications of graphene-based materials in flexible supercapacitors, a technological breakthrough is currently required to fabricate high-performance graphene paper by a facile method. Herein, highly conductive (similar to 6900 S m(-1)) graphene paper with loose multilayered structure is produced by a high-efficiency in-situ chemical reduction process, which assembles graphite oxide suspensions into film and simultaneously conducts chemical reduction. Graphene papers with different parameters (including different types and doses of reductants, different thicknesses and areas of films) are successfully fabricated through this in-situ chemical reduction method. Meanwhile, the influences of the graphene papers with different parameters upon the supercapacitor performance are systematically investigated. Flexible supercapacitor based on the graphene paper exhibits high areal capacitance (152.4 mF cm(-2) at current density of 2.0 mA cm(-2) in aqueous electrolyte), and excellent rate performance (88.7% retention at 8.0 mA cm(-2)). Furthermore, bracelet-shaped all-solid supercapacitor with fascinating cycling stability (96.6% retention after 10 000 cycles) and electrochemical stability (an almost negligible capacity loss under different bending states and 99.6% retention after 4000 bending cycles) is established by employing the graphene paper electrode material and polymer electrolyte. (C) 2017 Elsevier B.V. All rights reserved.