The ability of adsorption of chloride ion by calcium silicate hydrate(C S H) was tested by a chemical analysis method, and C S H structure was determined by nuclear magnetic resonance（NMR） spectroscopy and Raman spectroscopy The results show that the chloride ion adsorption ability of calcium silicate hydrate is closely related to its structure The calcium silicate hydrate with the average chain length of about 4 has the strongest chloride ion adsorption ability The cation of chloride salt promotes increasing average chain length of the calcium silicate hydrate, and enhances its chloride ion adsorption ability Compared with the sodium ion, calcium ion promotes better increasing average chain length of the calcium silicate hydrate, thereby adsorbing more chloride ions.