The hot forging of large-scale P/M TiAl alloy billet deformation was investigated based on a joint application of Deform-3D-based numerical simulation and physical simulation techniques. The temperature dependence on the thermal and mechanical properties of the billet was considered and the optimum hot working temperature of packed TiAl alloy was 1150–1200 °C. Based on the simulation, the material flow and thermo mechanical field variables, such as stress, strain, and temperature distribution were obtained and the relationships of load—displacement and load—time were figured out. To verify the validity of the simulation results, the experiments were also carried out in a forging plant, and a pancake with diameter of 150 mm was obtained exhibiting a regular shape.