Ring rolling process, especially hot rolling is characterized by 3D deformation, continuous change of thickness and height, high nonlinearity, non-steady flow and asymmetry. It involves both mechanical and thermal behaviors. Most mechanical and physical properties and boundary conditions are temperature related. The heat flow and stress analysis cannot be analyzed separately. In this study, both isothermal and coupled thermo-mechanical (CTM) 3D rigid-plastic finite element (FE) models of the hot ring rolling (HRR) process are developed to investigate their differences in accurately and quickly predicting the process. The results show that the latter should be more advantageous to the more accurate prediction and control of microstructure and properties of the ring.