The density-functional theory calculations in this work clearly revealed that the kuramite-structure Cu3SnS4 material possessing the metallic characteristic, result in the higher charge transfer between Iy ions and the Cu3SnS4 surfaces, and the rapid redox transfer reaction of I-3/I- in dye-sensitized solar cells system. Then, a feasible and mild solution method was proposed to in-situ synthesize Cu-rich kuramitestructure Cu3SnS4 thin film on FTO substrate, and the acquired thin film was used directly as counter electrode to assemble dye-sensitized solar cells without any post-treatments. The obtained-Cu3SnS4 nanosheet film had good bonding strength, expanded surface area, low photoelectron charge transfer resistance at the counter electrode/electrolyte interface, and great catalytic activity toward the reduction of I-3/I- ions. Power conversion efficiency of 7.80% was obtained by utilizing Cu3SnS4 nanosheet as counter electrode, which was superior to that of Pt electrode (6.52%). Our results demonstrate the earth abundant and low-cost kuramite Cu3SnS4 is an alternative Pt-free counter electrode material in dye sensitized solar cells. (C) 2016 Elsevier B.V. All rights reserved.