Hierarchical mesoporous γ-Fe2O3/carbon nanocomposites were prepared from metal organic frameworks (MOFs) MIL-100(Fe). The γ-Fe2O3/carbon nanocomposites and its precursor MIL-100(Fe) was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra (Raman), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry analysis (TGA) and N2 adsorption/desorption measurements. It is found that the as-prepared materials possess a hierarchical mesoporous nanostructure between the carbon and γ-Fe2O3 nanoparticles. When applied as cathode catalysts in rechargeable Li-O2 batteries, it is demonstrated from the galvanostatic discharge-charge process and cyclicvoltammetry (CV) that the electrode with γ-Fe2O3/carbon nanocomposites exhibits a lower charge and discharge over-potential, higher discharge capacity and better cycling stability than the pure Super P electrode, indicating its potential as a promising catalyst for Li-O2 batteries. The electrode with γ-Fe2O3/carbon nanocomposites shows a discharge capacity up to ∼5970 mAh g−1 carbon+catalyst at 0.1mAcm−2 and a high C-rate performance, and exhibits a very stable discharge voltage plateau of 2.7V and a charge voltage plateau of ∼3.75V. With the addition of γ-Fe2O3/carbon nanocomposites, the Li-O2 batteries can obtain good cycle performance over 30 cycles as confining the discharge/charge capacities to 600mA h g−1 carbon+catalyst.