Abstract: 30%Cr-Cu composites were prepared by spark plasma sintering process (SPS). The basic properties of the composite such as relative density, Brinell hardness and electrical conductivity were tested and the microstructures of the composites were observed. Hot simulation compression tests of the 30%Cr-Cu composites were conducted at deformation temperature of 650-950℃, strain rate of 0.001-10 s^-1 and deformation amount of 60% by the Gleeble-1500D thermal-mechanical simulation test machine. The true stress-true strain data of the 30%Cr-Cu composites were fitted, calculated and analyzed, constitutive equation of the composites was constructed, and the work hardening rate θ of the 30%Cr-Cu composite was obtained at the same time. The critical conditions of dynamic recrystallization during hot deformation of the 30%Cr-Cu composites were analyzed by computing the inflection point criterion of ln θ-ε curves and the minimum value criterion of -∂(ln θ)/∂ε-ε curves. The results show that the true stress-strain curves of the 30%Cr-Cu composites are mainly characterized by dynamic recrystallization softening mechanism. The peak stress increases with the increasing strain rate and the decreasing deformation temperature. The inflection point presents in the ln θ-ε curve and a minimum value appeas in the corresponding -∂(ln θ)/∂ε-ε curve when the critical state of the 30%Cr-Cu composites is attained, in which the strain that relates to the minimum value is the critical strain ε _c. The critical strain ε _c decreases with the increasing deformation temperature and the decreasing strain rate. The model of the critical strain with ε_c and Zener-Hollomon parameter can be described by the function of ε _c=2.38×10^-3 Z ^0.1396.