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Magnesium aluminate spinel (MgAl2O4) is widely used in steel metallurgy industry. Thermal conductivity at high tempera-ture significantly influences the cooling process of blast face and the heat preservation of steel converter. The effect of extal (temperature) and intal (antisite defect and grain boundary) factors on the thermal conductivity of MgAl2O4 was studied with non-equilibrium molecular dynamics. The main factors affecting the thermal conductivity of MgAl2O4 were summarized. In the temperature range of 100–2000 K, the results showed that the thermal conductivity of MgAl2O4 changed from 11.54 to 4.95 W/(m K) with the increase in temperature and was relatively stable at the temperature above 1000 K. The thermal conductivity of MgAl2O4 declined first and then rose with the increase in the antisite defects, and the minimum value was 6.95 W/(m K) at the inversion parameter i = 0.35. In addition, grain boundaries reduced the thermal conductivity of MgAl2O4 by 20％–30％ at temperature below 1000 K comparing with the non-grain boundary system. The grain bound-ary rotation angle at temperature above 1000 K had less effect on the thermal conductivity than that below 1000 K. Present simulation scheme for thermal conductivity of MgAl2O4 can also be applied to the study of other nonmetallic ceramics.