In this study, Fe3O4/graphene nanocomposite was synthesized through a liquid-phase co-precipitation method and characterized using X-ray diffraction and Fourier transform infrared spectrometer. The synthetic Fe3O4/graphene was used as a heterogeneous catalyst to activate persulfate to efficiently degrade methylene blue (MB). The target pollutant MB can be degraded by sulfate radicals depending on several parameters including persulfate and Fe3O4/graphene concentrations, pH and reaction temperature. Within 120 min of reaction time, almost 100% of 0.05 mM MB was removed by 1.5 mM persulfate in the presence of 150 mg/L of Fe3O4/graphene at pH = 6.0 and 25 degrees C. The degradation of MB was found to follow the pseudo-first-order kinetic model. The Fe3O4/graphene has much better stability and reusability than free Fe3O4 suggested by reuse tests. The results demonstrate that Fe3O4/graphene activated persulfate is a promising technology for remediation of water pollution caused by organic contaminants.