Abstract: Thermodynamic analysis was made to study the reduction volatilization of MgO in ludwigite by way of carbothermal reduction. The experimental results showed that the total mass loss rate of samples increases with rising temperature, of which the maximum is 61.8 wt% in the range from 1400°C to 1450°C. Magnesia in ludwigite was reduced and volatilized as gaseous magnesium vapour in the process of carbothermal reduction, and its mass loss rate went up to 98.0%. Magnesium was reoxidated into magnesia in the process of volatilization, where part of the volatilized matter formed the white feather-like crystal deposited on the bottom of furnace tube and the rest formed white powder deposited at the opening of furnace tube and adhered to tube wall together with boride/silicon volatilized. It was proved that there is volatilization of MgO from ludwigite in the process of carbothermal reduction.