Isothermal compression of HIPed(Hot Isostatic Pressed) FGH4096 superalloy in the temperature range 1080~1140℃ and strain rate range 0.02~1s-1 with deformation from 15% to 50% have been conducted on Gleeble-1500D simulator.Recrystallization nucleation and microstructure evolution during the hot deformation have been revealed by TEM(transmission electron microscopy) and MO(metallographic observation).When compressed with the deformation of 35% or blow,a not fully recrystallized microstructure called "Link" microstructure received.Fully recrystallized microstructure obtained when the deformation reached 50%,grain size of which grows as the temperature rise and strain rate decrease.Primary recrystallization nucleation sites could be summarized as follows: PPB(Previous Particle Boundaries),grain boundaries of the recrystallized grain and twin sourse.A fine structure with average grain size of 4μm obtained by the effect of multiaxial hot deformation as a result.