Aiming at the accurate microstructural control of turbine disk during hot forging, the evolution of microstructure under sudden increase of strain rate was investigated by finite element method. The constitutive models for flow stress, dynamic recrystallization and metadynamic recrystallization of a turbine disk material were implemented into finite element software. Then the hot compression of a cylindrical sample and single and multi-pass forging of a turbine disk were simulated. The results show that the sudden increase of strain rate can induce the occurrence of pseudometadynamic resrytallization. i.e., the suspension of dynamic recrystallization as a consequence of nucleation inhibition. The finite element method may have some shortcomings in microstructural prediction under sudden increase of strain rate. It is easier to achieve the target grain structure in the core area of turbine disk. The sudden increase of strain rate at key area should be avoided during single pass forging. The degree of recrystallization can be improved by multi-pass forging.