There are lots of semiconductor-graphene nanocomposites as promising electrode materials using in photovoltaic devices, because of their high conductivity and excellent eletrocatalytic activities. In this work, we have explored a facile one-step hydrothermal method to synthesize a novel composite which is assembled by In2.77S4 nanoflakes and graphene. This unique composite belongs to mesoporous materials and inherits many advantages from Indium sulfide and graphene. According to the results of cyclic voltammetry, electrochemical impedance spectra and Tafel polarization tests, the as-prepared In2.77S4 nanoflakes/graphene composites possess the commendable electro catalytic activity, charge transfer capability and electrochemical stability. In addition, when the obtained composites are used as counter electrode (CE) materials in dye-sensitized solar cells (DSSCs), the corresponding energy conversion efficiency is as high as 7.32%. This research provides a viable candidate for CEs of DSSCs and will contribute to developing other CE materials. (C) 2018 Elsevier Ltd. All rights reserved.