In order to study the effect of refractory graphite content and heating temperature on carbon pick-up of ultra-low-carbon steel from magnesia-carbon refractory, a transient axisymmetric mathematical model has been established. The momentum, heat and mass transfer between the refractory and the molten steel was modeled by using porous medium. Arrhenius law was employed to define the rate of the carbothermic reduction reaction of the magnesia. Besides, a series of experiments were carried out to verify the model. The results indicate that the carbon content of the molten steel rapidly rises when the refractory graphite content ranges from 3 mass% to 10 mass%, and the carbon pick-up induced by direct dissolution is significantly promoted. The influence of the heating temperature on the carbon content in the molten steel however is negligibly small, and the proportions of the carbon pick-up caused by the direct dissolution and the chemical reaction basically remain the same although the heating temperature increases by 100K. The effect of the refractory graphite content on the carbon pick-up of the molten steel far outweighs that of the heating temperature. (C) 2017 Elsevier Ltd. All rights reserved.