Graphene with flexible holey structure (HRGO) is firstly prepared by a wet chemical method in mild acid oxidation, and then graphene/manganese oxide hybrid nanocomposite with holey structure (HRGO/alpha-MnO2) is prepared by hydrothermally treating an isopropyl alcohol suspension of HRGO, MnCl2.4H(2)O, and KMnO4 at 90 degrees C for 1 h.alpha-MnO2 with needle-like morphology is uniformly dispersed on the surface of HRGO nanosheets, which prevents the restacking of the graphene nanosheets and allows graphene nanosheets to exist in a complete exfoliation state in HRGO/alpha-MnO2 hybrid material. The self-assembly between HRGO nanosheets and alpha-MnO2 particles can increase the specific surface area of the prepared material (about 196 m(2) g(-1)). The HRGO nanosheets improve the utilization efficiency of alpha-MnO2 in the hybrid electrode, while the holey structure provides a high density of porosity to facilitate charges and ions transport. The prepared electrode material exhibits a high specific capacitance of 348 F g(-1) at 5 mV s(-1) in 1 mol L-1 Na2SO4 electrolyte with a capacitance retention of 86% after 1000 cycles at a constant current density of 10 A g(-1). This preparation method may open new opportunity for preparing other types of graphene-based hybrid materials for technological applications. (c) 2014 Elsevier Ltd. All rights reserved.