Fe2O3 loaded porous graphitic carbon nitride (g-C3N4) photocatalysts have been prepared simply by thermal treatment in a hypoxia environment and the photocatalytic activities were evaluated in photocatalytic nitrogen fixation under artificial solar irradiation. Efficient reduction of dinitrogen to ammonia by photocatalysis over the hybrid catalysts was achieved even when the content of iron in the sample was less than 1 wt%, with an ammonia yield rate reaching 47.9 mg/L/h, 6 times higher than that of bare g-C3N4. The photocatalytic performance also outperforms many currently reported g-C3N4-based photocatalysts. X-ray photoelectron spectroscopy and M.ssbauer spectroscopy confirmed the formation of Fe2O3 in the photocatalyst and BET analysis revealed an enlarged pore volume by adjusting treatment temperature, providing benefits for photogenerated carrier separation and N-2 adsorption over the catalyst surface. Such g-C3N4 supported Fe2O3 nanoparticles with low-cost holds promise as one of the family member of photocatalysts for efficient N-2 fixation.