A model for simulating microstructure evolution during the rapid heating of reaustenitization for hypoeutectoid Fe-C steel has been developed using cellular automaton approach (CA). The prior microstructure strongly affects the as-quenched state and directly impact on the mechanical properties of finished components, and it can be predicted through austenite grain size and distribution, fraction of austenite, and chemical homogeneity. The kinetics of austenitization during the rapid induction heating is simulated by simultaneously considering continuous nucleation, grain growth and grain coarsening under various heating rates. The competition between the nucleation and grain growth of austenite grains in pearlite is revealed, and the simultaneous phase transformation from ferrite to austenite and the austenitic grain coarsening are also shown. The induction heating experiments are carried out to validate the model and the simulated results are good agreeable with the experimental measurement. The developed model can be used for optimizing the induction heating process in order to obtain finer prior austenite grains in the case depth.