The deformation behavior of GH625 superalloy was studied by the isothermal compression test in the temperature range of 950~ 1150 °C and the strain rate range of 0.001~5 s-1 and the effect of deformation condition on the microstructure was also investigated by OM and TEM. Results show that the dynamic recrystallization do not occur as the strain is little while the recrystallized grains appear when ε=0.1. As the deformation temperature increases, the recrystallized grain size increases and the dislocation density decreases; when the deformation temperature is low, some twins are observed in the matrix. As the strain rate increases, the nucleation rate increases and the grain size decreases, while the dislocation density increases at a constant deformation temperature; while at the low strain rate, the degree of recrystallization is high, which lead to the increase of grain size. According to stress-strain curves, the peak strain, the critical strain and the steady strain are obtained, and the relationship between the logarithmic values of the critical strain for DRX initiation () and the logarithmic value of the Zener-Hollomon parameter (lnZ) could be established as follows: lnεp= –6.022 85+0.123 85lnZ, εc=2.0×10-3·Z0.123 85. On the basis of quantitative microstructure analysis, the recrystallized volume fraction is also established as Xd=1–exp[–0.5634(ε/εp–0.79)1.313].