Abstract: A 12Cr1MoV steel pipe of the low temperature reheater in a circulating fluidized bed boiler of a power plant in Xinjiang suffered from perforation and leakage. Through macroscopic and microscopic morphology observation, chemical composition analysis, microstructure analysis, and hardness testing, and in combination with the actual working conditions on site, the corrosion perforation cause of the low temperature reheater steel pipe was analyzed. The results show that the metal chlorides generated by the coal combustion reacted with the oxide film, triggering "chlorine cycle and active oxidation". The dense protective film of Cr₂O₃ formed surface of steel pipe was destroyed and peeled off, and was difficult to form again in the hot corrosion environment, accelerating the corrosion of the matrix and causing perforation failure.