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 showed that with the increase of austenitization temperature,the grain size of the microstructure decreased,and the grain boundary morphology changed from curved to straight.The uniformity and stability of grain size were improved.At 1040℃,the austenite grain growth tendency and grain boundary morphology mutation were significant.The unmelted carbides are mainly M₇C₃ type,and their strong carbide elements Cr and Mo decrease with increasing austenitization temperature,while the content of V and Mn elements is relatively stable.After quenching and tempering,the phase consists of martensite,austenite,(Cr_2.5Fe_4.3Mo_0.1) C₃ and（Cr,Fe）₇C₃ type carbides.During the temperature rise process,the content of solid solution alloy and carbon element in the austenite phase increases,and the austenitization temperature characterized by quenching micro structure is more suitable between 1020℃and 1040℃.During the austenitization process,the activity of alloying elements is greater than zero,and the partial molar potential energy decreases with increasing austenitization temperature and is less than zero.