Abstract: The quenching process experiment of 0.22C−0.45Mn steel was carried out to study the effect of heating temperature and holding time on the average diameter of austenite grains, and to explore the growth behavior of low-temperature austenite grains of 0.22C−0.45Mn steel in the range of heating temperature (870−990 ℃) and holding time (15−120 min). Based on Beck, Hillert and Sellars models, the mathematical model of the average diameter of austenite grain was established respectively to predict the diameter of austenite grain of 0.22C−0.45Mn steel. The results show that with the increase of heating temperature, the austenite grain diameter of 0.22C−0.45Mn steel increases exponentially, and the growth rate accelerates. The growth rate of austenite grains slows down with the prolongation of holding time. Among the three grain models, Sellars model has the highest fitting accuracy and can better predict the austenite grain diameter of 0.22C−0.45Mn steel, which can provide a reference for the low-temperature heat treatment process of 0.22C−0.45Mn steel after rotational expansion in actual production.