In order to accurately predict the microstructure evolution during thermo-mechanical processing of AerMet100 ultrahigh-strength steel, the dynamic recrystallization (DRX) models including DRX volume fraction and DRX grain size were established by conducting a series of isothermal hot compression tests. The hot deformation behavior of the alloy in a wide range of temperatures from 800 ?C to 1040 ?C, strain rates from 0.01 s-1 to 10 s-1 and deformation degree from 15% to 60% were analyzed. The Zener-Hollomon parameter in the constitutive model for the AerMet100 steel was obtained to establish DRX models. The effects of deformation parameters on the microstructural evolution were quantitatively predicted through the established DRX models. The microstructure observations showed that higher temperature, lower strain rate and larger deformation degree were beneficial to obtaining the homogenization and refinement of the microstructure due to the occurrence of DRX. The good agreement between the prediction and the experiment validated the accuracy of the established DRX models. And the results indicated that the DRX models could be used to quantitatively predict the microstructure evolution of AerMet100 steel components during thermo-mechanical processing at different hot deformation conditions.