Abstract: In order to carry out the performance analysis of the heat generation element with outer casing, it is necessary to calculate accurately the outer surface temperature distribution of the element cladding. Due to the existence of fluid inside and outside the casing structure, the heat transfer situation becomes more complicated. Therefore, based on basic equations of heat transfer and the law of energy conservation, a special iterative algorithm and corresponding code were developed to solve the temperature distribution under this structure. Moreover, the code results were compared with results of Fluent simulation using a typical example. It shows that the relative error between results from the code and Fluent is within 5%. The module based on this algorithm can be coupled with the fuel performance code and promote the efficiency and accuracy of the analysis process.