Abstract: The temperature and strain profile of pellet and cladding were studied by developing a thermomechanic coupling code FROBA, which was based on analyzing fuel rod behavior theoretically during irradiation. Based on the analysis of results under different operating conditions, a numerical method for calculating fuel rod behavior was obtained, which could be used for the analysis of fuel component under operational conditions of nuclear reactors. The reliability of the code was also proved by comparing the results derived from Idaho National Laboratory software. The results show that the fuel temperature rises before irradiation. Once the densification is complete, the fuel temperature drops. After the gap closure occurs, the temperature gradually rises again.