Abstract: To solve the problems of air-lock, reduce the saturated vapor pressure and the temperature, which willbe generated in light oil lnloading system of rail tanker during light oil unloading process, mathematicalmodel for solving temperature field of the light oil in oil tanker and boundary condition is establishedthrough analyzing the geometrical characteristic of rail tanker.Simplifying the temperature field of light oiltanker as a two-dimensional non-steady heat transfer problem, ANSYS finite element software is adopted tosolve the mathematical model.By means of the software, either the temperature distribution of temperaturefield of light oil at any time of unloading duration can be obtained, or the temperature variables at any pointof tanker in wh0le unloading duration can be calculated.