Based on the theory of heat transfer and finite element (FE) theory, threedimensional (3D) transient nonlinear FE model of U75V heavy rail with 60 kg/m is established by using SolidWorks 3D modeling software. ANSYS Workbench was used to simulate numerically with FE the temperature field of the heavy rail during natural air cooling process. The results show that Heavy rail in the cooling process and the final cooling time, the temperature of the rail head is always the highest, and the waist of the rail and the bottom of the rail are reduced in turn, and the temperature at both ends is lower than that of the central part. Heavy rail in the cooling process and the final cooling time, its temperature of the crosssection is not the same, the main reason is due to heavy rail solid phase transition and heavy rail irregular crosssection of the impact.