Abstract: The in-situ TiB₂/Fe composites were synthesized by microwave sintering. The isothermal oxidation behavior of TiB₂/Fe composites was investigated in air at 500℃, 600℃ and 700℃. The surface, cross-sectional morphology and phase composition of the oxide films were also analyzed. The results show that the in-situ TiB₂/Fe composites are composed of TiB₂, Fe₂B and α-Fe phases. With the oxidation temperatures increasing, the oxidation weight of TiB₂/Fe composites increases obviously and shows the law of parabolic. At 500℃, the main oxidation products of the composites are Fe₂O₃ and Fe₃O₄. At 700℃, the oxides are composed of Fe₂O₃, TiO₂, Fe₉TiO₁₅ and Fe₃BO₆. With the increase of TiB₂ contents, the oxide particle size, oxidation mass and oxide layer thickness of TiB₂/Fe composites decrease at the same temperature, and the oxidation activation energy increases, which leads to the improvement of the oxidation resistance of TiB₂/Fe composites.