Abstract: The low temperature superheater tube of oil-fired boiler in a chemical plant cracked. The cracking reason was analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination,scanning electron microscope analysis and mechanical property test. The results show that the cracking reason of the low temperature superheater tube was that the pearlite spheroidization of the tube wall material seriously, the tensile strength and yield strength of the fire-facing surface of the tube wall reduced, and the heat resistance of the tube wall decreased, which led to the cracking of the low temperature superheater tube.