Based on the molecular dynamics simulation, the effect of four cations (K+、Na+、Ca2+、Mg2+) on the diffusion behavior and binding ability of chloride ions in the calcium silicate hydrate (C-S-H) pores is investigated. It is found that adsorption capacity of C-S-H for chloride ions is related to its adsorption capacity for cations. Ca2+ and Mg2+ can promote the adsorption of chloride ions, and the desorption of surface calcium in C-S-H can be easily facilitated into the solution, in which the spatial correlation between chloride ions and pore water is prolonged, resulting in the presence of multiple layers of hydration shells around chloride ions and the reduction of the diffusion ability. Under the combined actions of cations attracted by the C-S-H layer and water molecules, the diffusion coefficient of chloride ions in C-S-H pores is KCl > NaCl > CaCl2 > MgCl2.