The effects of NaNO2 on the passivation film were studied through X ray photoelectron spectroscopy(XPS) in the chloride environment of the mortar. The microstructural variation and characteristics of the passivation film of mortar in this condition were clarified. The results show that the intermediate products Na2FeO2 and (NaFeO2)2 are formed at the reaction of NaNO2 with Fe in alkaline environment, which promote the formation of Fe3O4 and enhance the effect of rust. The increase of NaNO2 content can promote the forward reaction process so as to increase the content of Fe3O4 in the passivation film. The percentage of Fe3+/Fe2+ on the surface of the passivation film is lower than that of Fe3+/Fe2+ at 5nm. That is to say, the internal density of the passivation film of steel is denser than that of the surface.