A kinetic model for the dissolution of the magnesia refractory in Al-killed steels was developed to predict the change of chemical compositions in the molten steel. Coupled reaction model and empirical equations were employed to calculate reactions between the refractory and the molten steel. The calculated result showed good agreement with the experimental value from the literature. The relationship between the mass transfer coefficient and the stirring energy dissipation in the molten steel was obtained as $$ k = \left( {5.6 - 4.7 \times e^{{ - 96.6\dot{\varepsilon }}} } \right) \times 10^{ - 4} $$ k = 5.6 - 4.7 × e - 96.6 ε ˙ × 10 - 4 m/s. The formation of spinels is dependent on the chemical composition of the molten steel. The MgO refractory may react with Al and O in the liquid steel. Meanwhile, the decomposing of the MgO refractory also plays an important role in the dissolution of the magnesia refractory in Al-killed steels.