Without considering the effects of alloying interaction on the Jominy end-quench curves, the prediction results obtained by YU Bai-hai′s nonlinear equation method for multi-alloying steels were different from those experimental ones reported in literature. Some alloying elements have marked influence on Jominy end-quench curves of steels. An improved mathematical model for simulating the Jominy end-quench curves is proposed by introducing a parameter named alloying interactions equivalent (L_e). With the improved model, the Jominy end-quench curves of steels so obtained agree very well with the experimental ones. Without considering the effects of alloying interaction on the Jominy end-quench curves, the prediction results obtained by YU Bai-hai’s nonlinear equation method for multi-alloying steels were different from those experimental ones reported in literature. on Jominy end-quench curves of steels. An improved mathematical model for simulating the Jominy end-quench curves is proposed by introducing a parameter named alloying interactions equivalent (L_e). With the improved model, the Jominy end-quench curves of steels so obtained agree very well with the experimental ones.