Abstract: In order to investigate the effect of Cr element on the plastic deformation process of structural steel, the uniaxial compression of low-carbon steel was carried out by Gleeble-1500 thermal simulation experimental machine.The deformation temperature was 730-1000℃, the strain rate was 0.01 -10 s^-1, and the total deformation was 0.8.The corresponding true stress-true strain curve and the thermal deformation structure were obtained.The high temperature deformation characteristics and the effect of alloying elements on the grain refinement were analyzed and discussed.The results show that due to the influence of Cr element, the flow stress variation trend of the two steels is different at 750-800 ℃.At the same time, the presence of Cr element improves the critical strain variable of dynamic recrystallization, which is beneficial to the nucleation of ferrite and inhibit the grain growth, which can play a role in grain refinement.