Abstract: By means of macroscopic examination, chemical compositions analysis, metallurgical examination, mechanical properties analysis and SEM fracture analysis, bursting reason of the high temperature steam injection pipe was investigated. The results show that the bursting was typical brittle fracture and the cracking originated from the two mechanical damages on the pipe surface. The bursting of high temperature steam injection pipe was mainly due to pipe wall thickness was uniform because of expanding diameter of pipe caused by huge stress of water hammer in the service process and the effective wall thickness was reduced because of the mechanical damages on the pipe surface.