The paper shows a finite element method (FEM) model to calculate the temperature distribution of desulphurizing lance use in hot metal pretreatment by ANSYS program. The dynamic temperature distribution under non-linear thermal loads within lance in one or more duty cycles is obtained. The temperature distribution at important parts of the lance changes with time and is summed up according to the simulation. Some important instructional opinions offered by the conclusion benefit the improvement of temperature-based structure design and mend of desulphurizing lance. In addition, the conclusion provides research data for thermal stress analysis of lance.