Hot deformation tests of 5CrNiMoV steel were performed at deformation temperatures of 700 to 870 °C and strain rates of 0.001 to 0.1 s-1 using the DIL 805D thermomechanical simulator. The critical strain and volume fraction models of Dynamic Recrystallization (DRX) were constructed based on the work hardening theory. The results showed that the critical strain of DRX decreases with increasing deformation temperature and decreasing strain rate, which implies that DRX occurs easily at higher temperatures and lower strain rates. The average DRX grain size model was established to predict grain size changes during hot deformation. Based on the hot processing maps that were constructed using the Dynamic Material Model (DMM) and microstructure observation, the optimum hot working parameters for 5CrNiMoV steel are a deformation temperature of 800–870 °C, a strain rate of 0.001–0.05 s-1.