Abstract: Calcium aluminum layered double hydroxides (CaAl-LDH) were prepared by co-precipitation and ion exchange method. The effect of CaAl-LDH on the chloride corrosion resistance of rebar in simulated concrete pore solution and the improvement of the service life of reinforced concrete in simulated marine environment were studied by electrochemical test method. The results show that the exchange between CaAl-LDH and chloride ion on the surface of rebar increased the passivation potential of rebar by nearly 200 mV, and the passivation range was expanded. CaAl-LDH could effectively reduce the chloride ion content in concrete, the chloride ion diffusion coefficient and the mass fraction of chloride ion on surface were reduced by 63.6% and 55.3% respectively, and the service life of reinforced concrete structure was prolonged.