Abstract: High temperature single-pass compression tests for 40CrNi2MoE steel was carried out on Gleeble-3800 simulator at the temperatures range of 1 123-1 423 K and the strain rate of 0.01-10 s-1. Based on the data of compression tests, the high temperature flow stress curves of 40CrNi2MoE steel were plotted, and the microstructure of the steel after deformation were observed. The results show that the flow stress and peak strain of the 40CrNi2MoE steel decreased with the decrease of strain rate and with the increase of deformation temperature. When the true strain was 0.9 and the range strain rate was 0.01-10 s-1, the full dynamic recrystallization temperature increased with the strain rate rising. When the strain rate was 10 s-1 and the deformation temperature was beyond 1 323 K, full dynamic recrystallization happened in the steel. The hot deformation activation energy of 40CrNi2MoE steel was 333.726 kJ·mol-1 by calculation. Then the hot plastic deformation constitutive equation and the relationship between the peak strain and Zener-Hollomon parameter were established.