Traditionally steelmaking reaction was analyzed by thermodynamics. However, steelmaking reactions are not reached to the equilibrium condition, in the industrial operation. In decarburization, the relation of carbon and oxygen contents is different from that calculated by the equilibrium under the atmospheric pressure. In hot metal dephosphorization, oxygen activity calculated by metal composition and that calculated by slag composition is widely different. Also, the inclusions with various compositions are observed in the ladle and their compositions differ from that of slag. Therefore, kinetic model is very important to understand the steelmaking reaction theoretically. For this purpose, the coupled reaction model proposed by Prof. D.G.C Robertson is the most important program and the author has been applied this model to the various steelmaking reactions. In this paper, some examples of the kinetic model to analyze the steelmaking process will be discussed.