Abstract: The ZnS/reduced graphene oxide (ZnS/RGO) composites were synthesized via a one-pot hydrothermal synthesis. The effects of solvent (ethanol, water) on the morphology and structure of ZnS/RGO composites were analyzed by XRD, FTIR, Raman and SEM. The results show that small ZnS particles uniformly disperse on the graphene sheet when using ethanol as the solvent during the formation of ZnS nanoparticles and the reduction of graphene oxide (GO) occur simultaneously. The photocatalytic activity of the prepared ZnS/RGO composite was examined by the degradation of Methylene blue (MB). The experimental results suggest that the designed ZnS/RGO composite possess superior photocatalytic activity, which is 3.7 fold higher reaction rates for MB degradation than that of the pure ZnS nanoparticles. Graphene, as a good electron collector and transporter to reduce the photoinduced electron-hole pair recombination, can greatly improve the photocatalytic activity of ZnS/RGO composites.