Chromite is an important raw material applied in refractories.Efforts have been made to obtain high-performance chromite by adding MgO and Al2O3 from the viewpoint of structure optimization.In order to explore the effect of Al2O3 and MgO on the structure,two formulas,i.e.,Mg-rich and Al-rich ones,were selected.The phase and microstructure development of samples heated in the temperature range of 1200-1600 ℃ were studied by X-ray diffraction and scanning electron microscopy with energy-dispersive spectrometry.MgO and Al2O3 added have diffused into chromite successfully by heat treatment.MgO diffuses into chromite,occupying the tetrahedral vacancies caused by the diffusion and oxidation of Fe2+ ions to stabilize the structure.Al2O3 diffuses into the surface layer of chromite,forming spinel-sesquioxide structure.Al-rich sample which has spinel-sesquioxide structure shows better corrosion resistance toward fayalite slag than Mg-rich sample which has single spinel structure by blocking the interdiffusion between Fe2+ ions in fayalite slag and Mg2+ ions in chromite.