Chloride-induced corrosion in reinforced concrete is a primary durability issue that causes large economic loss every year. To improve the intrinsic chloride binding capacity and realize a favorable corrosion protection of cement-based materials are thus crucial to prolong the service life of concrete structures. Here, alumina nano particles (ANPs) were incorporated to improve the chloride binding capacity of cement pastes in chloride solutions and the anti-corrosion performance of mortars under accelerated corrosion process. The ANPs facilitated the formation of alumino-ferrite-mono (AFm)-type phases, thereby improved the content of chemically bound chlorides. Solution calcium (Ca) ions benefited the chloride captured by calcium-(alumino-)silicate-hydrates (C-(A-)S-H) in the assistance of ANPs, especially at high initial chloride concentrations, and further evoked a pH-related chloride binding response. Moreover, the enhanced corrosion resistance was finally realized by incorporating appropriate amount of ANPs because of the filling and chemical effects induced low permeability of mortars. In general, the ANPs possess dual functions in the aspects of chloride binding and corrosion inhibition. These findings are expected to advance the design of high-durable cement-based materials serviced in the marine environment.