The　associated　effect　of　sodium　chloride　and　dihydrate　gypsum　on　the　mechanical　performance　of　a　slag-based　geopolymer　activated　by　quicklime　was　investigated　by　compressive　strength,　shrinkage,　and　square　circle　anti-cracking　tests　of　mortar　with　a　0.5　water-binder　ratio　and　a　1:3　binder-sand　ratio,　as　well　as　paste　soundness,　powder　X-ray　diffraction　(XRD),　thermogravimetric　analysis　(TGA),　scanning　electron　microscopy　with　energy　dispersive　spectroscopy　(SEM-EDS),　and　mercury　intrusion　porosimetry　(MIP)　of　the　paste.　The　results　indicate　that　(1)　when　dihydrate　gypsum　is　used　alone,　it　combines　with　calcium　aluminate　hydrate　(C-A-H)　to　form　calcium　sulfoaluminate　hydrate　(AFt),　which　encourages　the　hydration　process　of　slag.　A　7.5%　addition　can　result　in　an　increase　of　97.33%　and　36.92%　in　3-day　and　28-day　compressive　strengths,　respectively.　When　NaCl　is　used　by　itself,　it　facilitates　the　condensation　of　the　aluminum　silicate　tetrahedron　unit　and　generates　zeolite.　A　2%　dosage　can　lead　to　a　66.67%　increase　in　the　3-day　compressive　strength,　while　causing　a　15.89%　reduction　in　the　28-day　compressive　strength.　(2)　The　combined　effect　of　2%　NaCl　and　7.5%　gypsum　results　in　the　formation　of　needle-like　and　rod-shaped　AFt,　Friedel＇s　salt,　and　plate-like　Kuzel＇s　salt　in　the　geopolymer.　This　leads　to　an　increase　in　3-day　and　28-day　compressive　strengths　by　148%　and　37.85%,　respectively.　Furthermore,　it　reduces　the　porosity　by　18.7%.　(3)　Both　NaCl　and　gypsum　enhance　the　paste　soundness　of　the　slag-based　geopolymer,　and　they　do　no　harm　to　the　crack　resistance　of　the　geopolymer.　The　drying　shrinkage　of　the　geopolymer　at　28　days　is　just　0.48　x　10(-3),　which　is　only　66.7%　of　OPC.　This　slag-based　geopolymer　has　a　simple　preparation　process,　good　volume　stability,　low　raw　material　cost,　low　energy　consumption,　and　low　carbon　emissions.　It　can　be　used　instead　of　32.5　slag　Portland　cement　in　plain　concrete　applications,　and　has　high　engineering,　economic,　and　environmental　values.