Abstract: The microstructural characteristics of steel corrosion products in mortar under effect of carbonation and chloride salt environment were investigated by XPS and XRD. The results reveal that the peak value of iron in the corrosion products gradually increases from chloride salt and carbonization to the combination of chloride and carbonization, and the corrosion degree of reinforcement becomes more serious. In the course of corrosion, the compact structure of FeO and Fe₃O₄ on the surface of reinforcement will be transformed into Fe³⁺, and the Fe³⁺ would form the complex salt of Fe³⁺-Ca₂SiO₄ with the hydration products of Ca₂SiO₄. With the increase of corrosion degree of reinforcement, the salt content of Fe³⁺-Ca₂SiO₄ would gradually decrease, and Fe³⁺ would be transformed into Fe₂O₃ based other forms of rust.