The reinforced concrete that is used in structures constructed in coastal resorts and areas is impacted by chloride-induced corrosion by chlorine ions. Corrosion damage to such structures is often visible in rust-staining of the surface and cracking and spalling of the cover concrete due to reinforcement as a result of expansive steel corrosion This research conducted chlorine injure resistance of marine environment by the Durability improving Agent(DA) mixed with oligomer condensate and Si/Al composition. The DA countervails the drying shrinkage of concrete and mortar, fixes the chlorine ion, and prevents the erosion from the sulfate ion. In the experiments of this study, the concrete having excellent resistibility against salt damage was produced by mixing the DA with the OPC replaced the blast furnace slag. The whole 4 mixtures including the one mixed only with the cement (OPC) and another one replaced the blast-furnace slag (BSC), and the other one mixed with the 0.3% and 1.0% DA were tested. In all conducted experiments, the excellent resistibility against salt damages and drying shrinkage were identified in the order of DA, BSC, and OPC.