The work aims to find out the failure mechanism of internals in sulfur regeneration tower and put forward the so-lution to avoid the secondary failure. Visual inspection, metallographic microscope, energy dispersive spectroscopy (EDS) and other methods were used to analyze the corrosion mechanism of internals. EDS showed that the content of nickel in internal substrate was lower, but the content of sulfur in corrosion product was higher. The fracture of the internals was rough. Electron mi-croscopy and metallographic microstructure analysis showed that there were a large number of granular carbides precipitated at the grain boundary. The failure of the internals is induced by improper heat treatment which causes intergranular corrosion due to the precipitation of intergranular carbide. Meanwhile, the low content of nickel element also reduces the corrosion resistance of the material. Besides, the intergranular corrosion is accelerated by the corrosive medium containing sulfur. The 304 stainless steel internals with chemical composition meeting national standard should be used to avoid the precipitation of intergranular carbide due to improper heat treatment during production and use.