Flow behavior and dynamic recrystallization (DRX) critical conditions of 25vol.% B₄C_p/6061Al composite have been investigated by isothermal compression tests at temperatures ranging from 350℃ to 500℃ with strain rates of 0.001s_-1-1s_-1. The stress-strain curves show that DRX is the mainly softening mechanism of the composite, and an Arrhenius-type equation is developed used peak stress. Based on the strain hardening rate curves (θ-σ), the critical strains (ε_c) and critical stress (σ_c) are identified to express the initiation of DRX. The results show that there is a liner relationship between σ_c and σ_p: σ_c= 0.8374σ_p- 0.33708. The Zener-Hollomon parameter is also introduced to describe the effect of deformation conditions on critical conditions: ε_c=2.39×10_-4Z_0.11022. In addition, the steady-state strains (ε_ss) are determined by the θ-ε curves, and then the DRX diagram is established.