Abstract: The hot deformation characterishcs of Q235 class low carbon steel were investigated by plane strain compression test within the temperature range between 550℃ and 720℃, i.e. ferrite phase range, with a strain rate range of 5×10^-4 s^-1 to 10s^-1. The experimental results show that, in the ferrite phase range, the flow wstresses of strain-stress curves gradually increases to a peak followed by a strain softening and then a steady state at high strain, indicating that dynamic recovery or dynamic recrystallization occurs in the steel. The slower the strain rate, and/or the higher the deformation temperature, the smaller the strain corresponding to the peak stress. The hot deformation activation enemy (Q) of the steel tested is calculated to be 300.4 kJ/mol from the values of Zener-Hollomon parameters and peak stresses.