Abstract: Single-pass hot compression tests were carried out on 20Cr2Ni4A steel at deformation temperatures of 800-1 050 ℃ and strain rates of 0.01-5 s^-1 with thermal simulation test machine. The obtained true stress-true strain curves were modified by friction. According to the curves after frictional modification, the hot deformation behavior of 20Cr2Ni4A steel at high temperature was analyzed, the hot deformation constitutive model was constructed, and the hot processing map was drawn. The results show that the flow stresses calculated by friction modification were smaller than the measured stresses, and the difference between the two increased with the increase of strain. When the deformation temperatures were 850-1 050 ℃ and the strain rates were 0.01-0.1 s^-1, the dynamic recrystallization of the test steel during hot compression deformation was obvious. The hot deformation constitutive model could predict the peak stress of the test steel, and the average relative error between the predicted value and the measured value was 3.44%. According to the established hot processing map combined with the microstructure analysis, the optimum hot deformation parameters of the test steel were listed as follows: deformation temperatures of 875-925 ℃, strain rates of 0.01-0.02 s^-1 or deformation temperatures of 925-1 050 ℃ and strain rates of 0.01-1 s^-1.