Abstract: The nanoscale spinel structure metal oxide possesses broad application prospect due to its unique crystal structure and band structure. The MnFe₂O₄/reduced graphene oxide (rGO) nanocomposites were synthesized by hydrothermal method, the crystal structure, morphology, element distribution, binding energy and optical properties were characterized by XRD, high-resolution transmission electron microscope (HRTEM), energy dispersive X-ray spectrometer (EDX), FTIR, XPS, Raman spectroscopy (Raman), photoluminescence spectroscopy (PL) and UV-vis diffuse reflection spectroscopy (UV-vis DRS). The results show that the MnFe₂O₄/rGO nanocomposites prepared by this method have cubic spinel structure. The morphology is irregular ellipsoid with uniform particle size. MnFe₂O₄ nanoparticles loaded on the surface of rGO are partially coated with graphene, possessing small particle size and good dispersion. The MnFe₂O₄/rGO nanocomposites exhibit lower recombination efficiency of electron-hole pairs. The graphene has more defects and higher disorder degree. The oxygen-containing groups are partially reduced by polyvinyl pyrrolidone (PVP), and the quantity is greatly reduced. The band gap of MnFe₂O₄/rGO composite is narrower than that of pure MnFe₂O₄, resulting in red shift.