To study the fogging of GH4720Li nickel-based superalloy sufficiently, the hot deformation of the homogenization heat treated GH4720Li was carried out on Gleeble-3800 hot simulation experiment machine, and the microstructure evolution during high temperature deformation was also analyzed. Results show that the flow stress of GH4720Li at 1100℃/0.1s-1 is about 250MPa hich is sensitive to the deformation temperature and strain rate, also dynamic recrystallization is the main softening mechanism. Coarse grain improves the critical deformation temperature and strain rate for dynamic recrystallization, and complete dynamic recrystallization is obtained at 1140~1180℃ under strain rate of 0.001 s-1. The thermal deformation activation energy is calculated as Q= 1171 kJ/mol, and the higher thermal deformation activation indicates that the coarse grain is detrimental to hot workability and dynamic recrystallization for GH4720Li alloy. It is reveals that forging temperature for coarse GH4720Li alloy is determined above 1140℃, and low stran rate is necessary to ensure the occurance of dynamic recrystallization and dendrite broken.