It　is　widely　known　that　coastal　buildings　are　eroded　by　salt,　and　hygroscopic　performance　of　the　building　materials　significantly　affects　the　building　energy　consumption.　Therefore,　for　buildings　in　marine　atmospheric　zones,　it　is　necessary　to　explore　the　impact　of　salt　on　the　hygroscopic　properties　of　cement　mortar.　In　this　study,　cement　mortar　specimens　with　different　salt　contents　were　prepared　to　measure　their　hygroscopic　properties　at　different　humidity　levels,　and　acquire　the　regulation　of　equilibrium　moisture　content　with　changes　in　the　salt　content　and　relative　humidity.　In　addition,　based　on　a　variety　of　commonly　used　adsorption　formulae,　combined　with　the　influencing　factors　of　salt　content　proposed　in　this　study,　a　hygroscopic　fitting　formula　for　saltcontaining　materials　was　established.　The　experimental　results　revealed　the　following:　the　higher　the　salt　content,　the　longer　the　stability　time;　the　maximum　increase　in　moisture　absorption　occurred　in　the　early　stage　of　the　experiment,　which　gradually　decreased　and　tended　to　be　stable　in　the　later　stage;　at　any　level　of　relative　humidity,　the　equilibrium　moisture　content　of　the　specimen　increased　with　an　increase　in　the　salt　content,　and　the　promoting　effect　could　be　enhanced　by　more　than　three-fold;　furthermore,　the　maximum　moisture　content　appeared　under　conditions　of　high　salt　and　high　humidity.　In　addition,　the　fitting　formula　based　on　the　BET　formula　and　salt　influence　factor　had　a　good　fitting　effect,　and　the　goodness　of　fit　could　reach　0.98.