The Deform-3D software was employed to describe the microstructure evolution of a high Nb containing TiAl billet (Ti-42Al-8Nb-0.2W-0.1Y) during its hot pack-forging. To obtain the simulation parameters, hot compression tests were performed at temperatures of 1100~1250 °C and strain rates of 0.001~0.5 s-1. Dynamic recrystallization model was developed by using an undirected method, and the recrystallized volume fraction was described by an Avrami-type equation. The constitutive model of the flow stress of the alloy was established based on Cingara hardening equation and the dynamic recrystallization model. The simulated results indicate an inhomogeneous distribution of grain structure occurs due to friction, heat loss and single direction upsetting operation in forging process. The microstructure evolution of the present alloy during pack-forging is validated by comparing the simulated results with that of the experimental data. The result indicates that the implemented microstructure module can be effectively used to predict the microstructure evolution of the high Nb containing TiAl alloy during pack-forging