Considering the difficulty for the dynamic recrystallization to happen in Steel 26Cr2Ni4MoV, which was used to manufacture low-pressure steam turbine rotors generally, after-forging static recrystallization was studied with the thermo-torsion method. In order to investigate the influence of multi-step cumulative deformation on after-forging static recrystallization of Steel 26Cr2Ni4MoV, the thermo-torsion method was adopted to conduct a constant-temperature four-step torsion test at 900°C. The time gap between each step in the test agreed with that in real production. Results show that the influence of multi-step cumulative deformation on after-forging static recrystallization is almost the same with that of single-step deformation. It means that the nucleation and the growth of after-forging static recrystallization are related mainly to the last deformation and temperature-keeping time. Grain size can be controlled through the last deformation and temperature-keeping time. The findings supply the theoretical foundation for the said-steel controlled forging processes.