A thermal-mechanical model was developed to describe semi-solid thixo-forging process with high solid fraction,including temperature field,maximum/minimum temperature distribution,moving speed of the mould as well as forming force.The simulated results reveal that occurrence of conventional hot-forging can be observed during thixo-forging,meanwhile,high forging speed can decrease forming force,which can result in the liquid-solid phase separation in the billets.The simulated maximum forming force is well in agreement with experimental one,showing the availability of the model,however,there exists the difference in forming force during thixo-forging,which means the model need be further optimized.