Abstract: In order to accelerate the impact of simulated marine tidal zone environment on the durability of concrete, the mineral powder and nano modified mineral admixture were added, and the effect of dry-wet cycling of NaCl on the resistance to chloride ion erosion and microstructure of concrete was studied, which was compared with the immersion test. The results show that the dry-wet cycling coarsens the pore structure of the concrete surface, increases the pore content of pore size larger than 50 nm and significantly increases the free and total chloride ion concentration; the incorporation of nano-modified mineral admixture can reduce the internal porosity of concrete and the harmful pore content, while can improve the chloride ion binding capacity of concrete. After 60 days of wet and dry cycling, the Ca(OH)₂ on the surface layer is gradually consumed, and the Friedel salt and CaCO₃ are formed.