Abstract: The influence of austenitization temperature on the microstructure and thermodynamics of DC53 steel was investigated using OM, SEM, Jmatpro software calculation, and Image proplus 6.0 analysis. The results indicate that the grain size and content of unmelted carbides decrease with increasing austenitization temperature; The uniformity of grain size increases relatively with the increase of temperature, and the grain boundary morphology changes from curved to straight shape, and the stability of grain size increases; At a temperature of 1040 ℃, there is a significant change in austenite grain growth tendency, grain boundary morphology, and internal point like carbide content. The austenitization temperature is more suitable when the quenched microstructure is between 1020 ℃ and 1040 ℃. After quenching and tempering, the phase consists of martensite, austenite, (Cr2.5Fe4.3Mo0.1) C3 and (Cr, Fe) 7C3 carbides. The unmelted carbides are mainly M7C3 type, with alloy element activity greater than zero and partial molar potential energy decreasing with increasing austenitization temperature and less than zero; During the temperature rise process, the solid solution alloy and carbon element content in the austenite phase increase, while the strong carbide elements Cr and Mo in M7C3 type carbides decrease, while the content of V and Mn elements remains relatively stable.