Abstract: The steel cylindrical shell of eight phosphor-making furnace bursted one after another after nine to ten years service in one phosphor-making furnace. By means of macroscopic examination, metallographic examination, fracture analysis, chemical composition analysis and so on, the shell burst reason was analyzed. The results showed that because of high temperatures of phosphorus combustion and repeated start and stop operation of phosphor-making furnace, the embrittlement effects such as hydrogen damage of shell material, pearlier spheroidization, large grain size and strain aging led to the shell thinning by phosphoric acid, together with the results of thermal expansion and contraction joint action of stress, the shell bursted at last.