Abstract: A thermo-mechanical coupled 3D finite element simulation was carried on the whole rolling passes of U71Mn heavy rail. The model of the rolled-piece was established by extracting and stretching the middle cross-section grid, and the temperature data were loaded according to the corresponding relations of nodes positions before and after. The infrared thermometer was used to carry out the online temperature measurement of the rolled-piece surface and the results were compared with the simulated ones. The results show that the temperature distribution of the rail cross-section was extremely complex because of its irregular shape. As the rolling progress went on, temperature at the surface of the rolled-piece especially corners dropped heavily, temperature raised first and then declined at the heart of rolled-piece, there formed two high temperature area eventually at the middle of the rail head and base. The measured temperature was consistent with the simulated one, this proved the validity of the model.