This research work presented the analysis of plasticity of high carbon alloy constructional steel in the conditions corresponding to plate rolling in a reversing mill. The deformation and temperature conditions occurring in the real process were reproduced during testing. Plasticity of the steel in the temperature range of 800÷1000oC and for three different strain rates of 0.1, 1.0 and 10 /s was determined in the course of experiments. The research was carried out using the Gleeble 3800 physical simulator of metallurgical processes with the Pocket Jaw module, to estimate the steel plasticity in the uniaxial tension test to the failure strain of the sample. The performed research work enables to determine the optimum temperatures and size of the critical deformations which should be taken into consideration when designing the process of the tested steel rolling in order to avoid formation of internal and external cracks.