A novel facile combination of precipitation and plasma discharge reaction is successfully employed for one-step synthesis of an α-Fe₂O₃–Fe₃O₄ graphene nanocomposite (GFs). The co-existence and anchoring of hematite (α-Fe₂O₃) and magnetite (Fe₃O₄) nanoparticles onto a graphene sheet in the as synthesized GFs were verified by results of XRD, Raman, SEM, TEM, and XPS. HRTEM characterization was used for confirming the bonding between α-Fe₂O₃/Fe₃O₄ nanoparticles and the graphene sheet. Consequently, GFs shows superior photodegrading performance towards methylene blue (MB), compared to individual α-Fe₂O₃/Fe₃O₄ nanoparticles, as a result of band gap narrowing and the electron–hole pair recombination rate reducing. Moreover, GFs allows a good possibility of separating and recycling under an external-magnetic field, suggesting potential in visible-light-promoted photocatalytic applications.