Abstract: By applying Gleeble-3800 Thermal Simulation Tester, we study the thermal deformation behavior of micro-carbon steel at temperatures of 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ and under the conditions of 0.01 s^-1, 0.1s^-1, 1s^-1. The temperature deformation constitutive equation is constructed by analyzing the characteristics of the deformed structure. The results show that the flow stress of micro-carbon steel increases with the rising strain in the initial stage of deformation, and gradually stabilizes after the peak. When the temperature is higher than 750℃, there will be obvious processing softening. With the Sellars-Tegart equation, the heat deformation activation energy Q of micro carbon steel was obtained by fitting the parameters of the model to 364.894 kJ/mol. A flow stress model is established.