To improve the hot workability of hard-deformed superalloy U720Li, the effect of holding time before deformation (5 min and 10 min) on its hot deformation behavior was investigated using hot compression tests. The flow stress increases with increase of strain rate, while decreases with increase of deformation temperature and holding time. Based on the obtained Arrhenius-type constitutive models, the calculated peak stresses are in good agreement with experimental values, and the deformation activation energies for the holding time of 5 min and 10 min were calculated to be 992.006 kJ·mol-1 and 850.996 kJ·mol-1, respectively. Moreover, processing maps of U720Li alloy at these two holding time were constructed. Through observation of deformation microstructures in each domain of the processing maps, the optimal hot working conditions for the holding time of 5 min were determined to be 1090~1110 ℃/1~10 s-1 and 1146~1180 ℃/1~10 s-1, while those for the holding time of 10 min were 1080~1090 ℃/1~10 s-1 and 1153~1160 ℃/1~10 s-1. This indicates that the “safe” processing window can be obviously enlarged by shortening the holding time reasonably. In the absence of cracking, the dynamic recrystallization (DRX) grain size increases gradually with increasing deformation temperature and holding time, but it first decreases and then increases with the increase of strain rate. When the deformation temperature is below 1100 °C, the DRX mechanism is mainly the particle-induced continuous dynamic recrystallization (PI-CDRX). But as the temperature was raised to above 1130 °C, the main DRX mechanism changes to discontinuous dynamic recrystallization (DDRX).