Analyzing the interface reaction and thermal stress distribution between materials and slag, the damage mechanism of MgO-CaO refractory in the air gun area of the argon oxygen decarburization furnace (AOD furnace) was investigated. The study of the interface reaction between MgO-CaO refractories and slag finds that the slag preferentially reacts with CaO in the material to form tricalcium silicate (C₃S) and dicalcium silicate (C₂S). Meanwhile, the dissolution rate of these two products into the slag is much larger than that of MgO and CaO, which is prone to producing liquid. The study of the thermal stress distribution in the air gun area finds that when the hot face of the air gun brick reaches 1 730 ℃ and the average temperature of the cold face is 150 ℃, the introduction of cold airflow creates a great temperature gradient within the MgO-CaO refractory in the air gun area. This causes the maximum thermo-mechanical stresses in the material at a depth of 8 mm from the hot surface. Based on the interface reaction and thermal stress distribution results, it can be inferred that the MgO-CaO refractory in the air gun area bears the maximum thermal stress at a distance of 8 mm from the hot surface during high-temperature service. This leads to stress concentration and crack formation in this area. At the same time, the C₃S and C₂S generated by the interface reaction between slag and refractory quickly dissolve into the slag, significantly reducing the high-temperature strength of the material. Under the combined action of slag erosion and thermal stress accelerate cracks, accelerating structural spalling, which occurs cyclically during the smelting process and ultimately damages MgO-CaO refractory in the air gun area of AOD furnace.