Abstract: Using numerical calculation method by CAESAR Ⅱ V 5.0 pipe stress analysis program, the displacement change of different wall thickness of high temperature reheat steam pipelines in a power plant was simulated, and the constant of constant force hanger was measured in the field. The results showed that the main causes of abnormal thermal displacement of high temperature reheat pipe were due to deviation of pipe wall thickness and unqualified constant of constant force hanger. After adjusting for the hanger, the sinking problem of pipe was resolved.