Abstract: Leakage occurred to the G102 steel pipe of the final reheater in a large thermal power plant. The causes of leakage were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscopy and energy spectrum analysis, and mechanical property test. The results show that the G102 steel pipe section of the final reheater had been running for 160,000 hours, and the structure was aging and the performance was seriously degraded. The oxide skin of the inner and outer walls of the G102 steel pipe section affected the heat exchange, increased the temperature of the metal wall, accelerated the aging of the material structure and the deterioration of the performance, and finally made the G102 steel pipe reach the later stage of creep life and leak. The design and structural factors also accelerated the aging and performance degradation of the material. Finally, some suggestions were put forward for the safe and stable operation of the G102 steel pipe of the final reheater.