Abstract: The manual high-temperature valve at the outlet of a sulfur incinerator in a certain factory broke after one month of use. The causes of the fracture of the high-temperature valve were analyzed by macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscopy and energy spectrum analysis and finite element analysis. The results show that there were serious non-metallic inclusions and a large amount of carbides in the valve shaft of the high-temperature valve, which reduced the corrosion resistance of the material. In the actual operation process of the incinerator, the working stress of the high-temperature valve had exceeded the yield strength and strength limit of the material, ultimately led to the fracture of the high-temperature valve.