Abstract: A microstructural prediction model of low carbon Nb-containing steels based on the interaction of precipitation, recovery and recrystallization was developed to simulate the evolution of precipitation and recrystallization of coarse-grained austenite in low carbon Nb-containing steels during pass interval of hot deformation. The application of this model in making the recrystallization-precipitation-temperature-time diagram (RPTT) of low carbon Nb-containing steels was discussed. The simulation results are well coincident with the experimental data of two low-carbon Nb-containing steels, indicating that the behaviors of precipitation and recrystallization can be predicted using this model for different low carbon Nb-containing steels at various processing conditions.