Abstract <p>The Ti–6Al–4V seamless tube’s performance is significantly influenced by its hot continuous rolling and reducing-sizing deformation process. A study involving hot compression experiments on this tube with a microstructure formed upon continuous cooling to two-phase region led to the development of a high-precision segmented constitutive model. This model integrates dislocation density theory with the recrystallization softening mechanism to simulate and analyze the microstructure evolution in the course of deformation process. The results identified the transition of the hot deformation mechanism in the Ti–6Al–4V seamless tube within the two-phase region from dynamic recrystallization (DRX) to dynamic recovery (DRV) as temperature increases and strain rate decreases. In the upper two-phase region, deformation is governed by DRX in β grain, α grain-boundary fragmentation, and discontinuous dynamic recrystallization (DDRX) in partially precipitated lamellar α phase. Conversely, in the lower two-phase region, the continuous dynamic recrystallization mechanism of lamellar α phase works. Adiabatic shear and local flow instability are prone to occur under high strain rate conditions, causing microstructural unevenness. It is concluded that the optimal hot working conditions are a deformation temperature of 850–920°C and a strain rate between 0.01 to 1 s^–1.</p>