Abstract: ESPRESSO sodium loop was made for the test and thermal shock which was for the Italy PEC Fast Reactor fuel components. More than 10 years has passed since the loop was imported from Italy, and its life-span and performance are not assured as same as the design parameters. At the same time the disassemble and installing of the loop influenced the safety of the loop operation badly which was high-temperature plant because of the difference of the jointing quality and inspection standard. Through the pipeline stress analysis and calculation, we can verdict the distribution of the pipeline stress, and the loop operation safety is ensured by adjusting the constant hangers.