Thermodynamic parameters of chloride and sulfate intercalated hydrotalcites were deduced. The phase evolutions in alkali-activated slag cement upon only sodium chloride or only magnesium sulfate attack and combined attack of those two salts were investigated via thermodynamic modelling. Friedel's salt was predicted to form under sodium chloride attack， while monosulfate， ettringite， gypsum， magnesium silicate hydrate and sulfate intercalated hydrotalcite were predicted to form upon magnesium sulfate attack. The combined attack of sodium chloride and magnesium sulfate exhibited not only characteristics by single attack of those two salts but also coupling effects which promoted the formation of chloride intercalated hydrotalcite and inhibited the formation of Friedel's salt and magnesium silicate hydrate. An increase of the magnesium sulfate proportion led to lower capacity of chemically binding chloride.