Abstract: The flow stress behavior of 10B06 cold heading steel continuous casting billet during hot compression deformation was studied by an MMS-200 thermal simulation test machine at deformation temperatures ranged from 750 ℃ to 1 100 ℃ and strain rates ranged from 0.01 s-1 to 20 s-1. The strain hardening index and thermal activation energy of the steel were determined by linear regression analysis, and the flow stress constitutive equation of this steel was also obtained. The results show that the flow softening behavior of the steel during hot compress deformation was the result of combined effects of dynamic recrystallization, dynamic recovery and work hardening. Soften effect was dominated by dynamic recrystallization at lower deformation temperatures and smaller strain rates, and by dynamic recrystallization and recovery at higher deformation temperatures and larger strain rates. A function of Zener-Hollomon parameter was used to describe the flow stress of the steel, and the thermal activation energy was 220.132 3 kJ·mol-1.