The deterioration of the durability of marine concrete and the degree of corrosion of internal steel bars in the tidal, splash and atmospheric zones are often serious in salt spray wetting and drying cycle. The diffusion of chloride in cement-based materials was investigated at different parameters (i.e., mix ratio, dry-wet ratio, and exposure time) by a cycle test of salt spray wetting and drying and a test method of layered grinding and potentiometric titration. The results show that the deposition and transport of chloride ions in mortar are primarily affected by salt spray wetting-drying cycle, dry-wet ratio, water-binder ratio, and exposure period. The influence of water-binder ratio is dominant, while the influence of dry-wet ratio is slight. The maximum concentration of chloride Cmax and the effective chloride diffusion coefficient Deff increase as water-binder ratio improves. Cmax firstly increases and subsequently declines as fly ash amount and frequency of dry-wet cycles increase. Deff decreases as exposure time increases. Deff firstly increases and subsequently reduces as fly ash content increases. Low water-binder ratio and use of fly ash can effectively postpone chloride erosion, thereby enhancing the durability of structures.