Abstract: Austenite grain growth behavior of DP590 dual-phase steel was studied and the influence rule of heating rate on the initial grain size was analyzed by changing the heating rate and heating time. The initial grain size decreases with the heating rate increasing and finally comes to a constant. When the soaking time is long enough, the austenite grain size increases and tends to remain unchanged. These experimental data were fitted by the Sellars model. In order to avoid the deviation caused by model parameters, a new data processing method was proposed. With this method, the models of initial austenite grain size and austenite grain growth were built. It is found that the model parameters are much more reasonable and reliable, and the calculated data is in good agreement with the experiment data.