Abstract: A mathematical model was established and applied to simulate the decarburization in RH degasser and to study the effects of [C]₀,[O]₀, flow amount of Ar and diameter of the snorkels on the decarburization. The results obtained by using the model showed that as considering the RH process in the plant, the oxygen in the melt at the end of decarburization can be reduced by increasing the original carbon and decreasing the original oxygen without unacceptable carbon content. Thus the consumption of deoxidizing alloy can be reduced, and the inclusions produced in deoxidizing process can be reduced.