Abstract： The experimental data obtained by hot compression experiment were used to establish a Q550D low carbon bainite steel dynamic recrystallization model and a cellular automata model. The microstructure evolution on the hot deformation process was simulated by using DEFORM3D finite element software. The simulation results show that the strain rate at a temperature of 1 150 °C for the 0.05 s-1 sample in the process of hot deformation microstructure have dynamic recrystallization and the grain size is refined. At a temperature of 1 050 °C when the strain rate is increased, the dynamic recrystallization austenitic grain size decreases. The simulation results agrees with the experimental results.