Abstract: With the rapid development of the domestic automobile industry, the quality of automobiles are in increasingly higher requirement. Automobile gears are one of the key parts in the automobile manufacturing industry, but the high-quality gear steel still needs to be imported from abroad in China. The austenite grains and precipitated secondary phase particles of gear steel have a great influence on its properties, but in the production process of gear steel, the change of austenite grains and the control of secondary phase particles are very complex. Therefore, in this paper, the austenite grain size, the austenite growth mechanism and model, the pinning force and model of the secondary phase particles of Nb (C, N) and AlN, and the influence of temperature on the austenite grain size and secondary phase particle size are reviewed. The austenite grain growth law and the secondary phase particle control method are illustrated, which will provide the reference to produce high-quality gear steel.