VS4/reduced graphene oxide (VS4/rGO) composites are successfully synthesized via a one-step hydrothermal route. Then their photocatalytic activities are examined by water splitting reaction, and the morphology and structure are characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy and thermo gravimetric analysis, respectively. It is shown that graphene accelerates the nucleation during the growth period of VS4. Main product is VS4, not VS2. Monoclinic VS4 particles interact with graphene through chemical action. VS4/rGO composites show excellent photocatalytic water splitting activities under visible-light irradiation. This excellent performance is due to the formation of pi-conjugated structure, which can transmit electrons from S2(p) to graphene rapidly. However, composites with excess graphene show poor dispersion, which leads to the best doping ratio of graphene is 5 wt%. Copyright (c) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.