To explore a green and low-carbon scheme for self-compacting concrete, a comparative study on the chloride ion erosion resistance of self-compacting alkali-activated concrete and self-compacting cement concrete was conducted using the dry-wet cycle accelerated test method. The free chloride ion content, total chloride ion content, chloride ion binding capacity, and apparent chloride diffusion coefficient of concrete were analyzed. The results indicate that when the chloride ion erosion duration and depth are constant, the free chloride ion and total chloride ion contents are the highest in self-compacting cement concrete, followed by self-compacting alkali-activated concrete, and the lowest in self-compacting alkali-activated concrete modified with 2% nano-SiO₂. The chloride ion binding capacity of self-compacting alkali-activated concrete is 29.90% higher than that of self-compacting cement concrete, and its apparent chloride diffusion coefficient is lower, demonstrating superior resistance to chloride ion erosion. Although the incorporation of nano-SiO₂ reduces the chloride ion binding capacity of self-compacting alkali-activated concrete, it also contributes to a decrease in the apparent chloride diffusion coefficient.