Magnesium-calcium refractory is considered to be an ideal lining material for off-furnace refining equipment due to its high refractoriness, stable thermodynamic properties, and purification of molten steel. However, in the actual smelting process, it has been eroded by low basicity slag for a long time, and the melting loss is serious. Therefore, in order to improve the corrosion resistance of MgO-CaO system to low basicity slag. In this paper, light-burned dolomite powder and light-burned magnesium oxide powder were used as the main raw materials, and different amounts of nano-Cr₂O₃ (0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0%, mass fraction) were added. After mixing, molding and firing at 1 650 ℃×3 h, the erosion experiment of low basicity slag (m(CaO)∶m(SiO₂)=1∶1) was carried out. The phase composition and microstructure of the samples after erosion were analyzed by XRD and SEM. The results show that the addition of a small amount of nano-Cr₂O₃ will dissolve into CaO and MgO grains, causing lattice distortion and promoting sintering. When the addition of nano-Cr₂O₃ exceeds 2.5%, nano-Cr₂O₃ will react with CaO and MgO to form CaCr₂O₄ and MgCr₂O₄, which are filled in the grain boundaries and other parts of the grains. The microstructure of the sample is changed, and the corrosion resistance of the sample is significantly improved.