Abstract: The hot compressive experiment of Cr9Mo high-alloy steel was carried out on Gleeble-1500D thermo-simulation machine.The hot plastic behavior of the steel was investigated at temperatures ranging from 1 173 to 1 473 K and strain rates from 10-3-1 s-1.Based on the theory of the classical stress-dislocation relation and the kinematics of the dynamic recrystallization,the flow stress constitutive equations in the work hardening-dynamical recovery stage and dynamical recrystallization stage were established for Cr9Mo steel,respectively.The stress-strain curves of Cr9Mo steel predicted by the established models were in basic agreement with experimental results,indicating that the equation could predict the high temperature rheological behevior.