Nickel-based alloy is a good choice for materials used in ultra-supercritical power plant, which is subjected to high temperature about 700 ℃ and high pressure in service. In order to meet the requirements above, a nickel-based alloy was designed and the tubes were successfully manufactured. Based on the hot/cold working processes of tube components of the nickel-based alloy, microstructural evolution, especially the recrystallization mechanisms during hot working processes of the alloy were systematically investigated by using a series of hot compression tests, solution annealing tests, OM and TEM analyses. The results showed that dynamic recrystallization was dominated by discontinuous dynamic recrystallization mechanism involving grain boundary bulging, whereas the nucleation mechanism with strain inducing grain boundary migration was the driving force of static recrystallization. In addition, the essence of different forms of step grain boundary producing during dynamic recrystallization and static recrystallization was to make the surface deviate from low index surface, which could ensure more interface to be low energy close-packed surface, so that the energy of grain boundary interface would be reduced. The morphology of step grain boundary depended on the crystallographic relationship of crystal interface and the Burgers vector of grain boundary dislocation. Moreover, the presence of step grain boundary could also promote grain boundary migration and accelerate the recrystallization process. When the recrystallization process was completed, step grain boundaries still remained partially to minimize interfacial energy and continue to promote subsequent grain growth processes.