Abstract: The bursting reason of 12Cr1MoV steam pipe was investigated by means of chemical composition analysis, metallographic examination, high-temperature tensile tests and field investigation. The results showed that the pearlite spheroidization grading was 4.5 grade. The high-temperature strength and high-temperature lasting strength of material was lower than that in normal condition. It was concluded that long-time overheating was the main reason of the bursting failure.