Abstract: Abstract The 15CrMoG steel soot blower gun barrel of a certain unit broke. The cause of barrel fracture was analyzed using macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscopy and energy spectrum analysis. The results show that the horizontal height outside the soot blower furnace was too low, which caused the accumulate of liquid inside the soot blower barrel, resulted in the entry of furnace flue gas into the barrel. The flue gas combined with residual steam to form a corrosive medium and accumulate, resulted in low-temperature sulfur corrosion of the soot blower barrel, severe thinning of the barrel, and ultimately led to barrel fracture.