To investigate the influence of chemical components in slag concrete on its resistance to chloride ion attack, this study took two types of slags (A and B) with different mineral components and four types of cements (W, X, Y, and Z) as raw materials to prepare slag concrete samples with a fixed slag replacement rate of 60%. The adsorption and diffusion characteristics of Cl- in the concrete under different cement-slag combinations were studied through X-ray diffraction analysis, thermodynamic modeling, and mercury intrusion porosimetry tests. The experimental results indicate that adding slag can enhance the Cl- adsorption capacity of concrete and reduce the diffusion rate of Cl-. Compared to slag concrete with lower aluminum content, slag concrete with higher aluminum content exhibits stronger Cl- adsorption capacity. The concrete prepared with cement W has the strongest Cl- adsorption capacity, while that prepared with cement Z has the weakest Cl- adsorption capacity. C3A and C3S significantly influence the Cl- adsorption capacity. Higher pH decreases the Cl- adsorption capacity. The formation of carboaluminates, the filling effect of limestone, and the reduction in pore size all contribute to lowering the permeability of Cl-.