Abstract: The dynamical recrystallization (DRX) behavior of 9Ni steel was investigated via a single-pass reduction test on a MMS-300 simulator over the temperatures range from 800 to 1150°C at the strain rates range from 0.05 to 1s^-1. The critical conditions for DRX and peak stress/strain were determined by the relationship between work hardening rate (θ) and flow stress (σ). The material parameters in the hyperbolic sine constitutive equation were determined with regression analysis, and the DRX activation energy was thus obtained to be 269kJ/mol. The relationship between critical strain, peak strain/stress and the dimensionless parameter Z/A were established by linear regression. Mathematical model of the DRX kinetics was developed for low-carbon 9Ni steel by using Avrami equation and stress-strain curses.