Abstract: P110 steel was nitrided in salt bath at 490 ℃ for 4 h. The effect of nitriding on micro-structure of P110 steel was studied by optical microscope, X-ray diffractometer and scanning electron microscope. The influence of elemental sulfur on the corrosion behaviors of nitrided and non-nitrided samples were studied by using four different sulfur corrosion media. The results showed that the structure of percolating layers of P110 steel were oxide layer, compound layer and diffusion layer from the surface to the inside after nitriding treatment, and the compound layer was mainly composed of Fe₂C, Fe₂N and Mn. The compound layer is dense in structure, which can protect the steel substrate well and improve the sulfur corrosion resistance of P110 steel.