This　study　develops　an　alkali-activated　slag-electric　furnace　nickel　slag　(AAS-ENS)　composite　system　by　incorporating　electric　furnace　nickel　slag　(ENS)　and　granulated　blast　furnace　slag　(GBFS)　to　explore　a　sustainable　and　high-value　utilization　pathway　for　ENS.　The　Ca/Si　and　Si/Al　ratios　of　the　precursor　materials　were　adjusted　by　controlling　the　GBFS　dosage,　and　their　effects　on　the　compressive　strength,　flexural　strength,　and　microstructure　of　AAS-ENS　composites　were　systematically　investigated.　The　results　indicate　that　compressive　strength　exhibits　a　quadratic　relationship　with　the　Ca/Si　ratio,　with　an　optimal　range　of　0.35–0.45.　Additionally,　the　Si/Al　ratio　shows　a　negative　correlation　with　compressive　strength,　with　the　optimal　Si/Al　ratio　estimated　to　be　below　4.　Microstructural　analysis,　including　heat　of　hydration,　X-ray　diffraction　(XRD),　thermogravimetric　analysis　(TG-DTG),　mercury　intrusion　porosimetry　(MIP),　and　scanning　electron　microscopy　(SEM),　revealed　that　properly　balanced　Ca/Si　and　Si/Al　ratios　promote　the　formation　of　C-(A)-S-H　gel,　leading　to　higher　material　density　and　improved　mechanical　performance.　These　findings　provide　a　theoretical　foundation　for　optimizing　the　mechanical　properties　and　microstructure　of　AAS-ENS　composites　and　offer　practical　insights　into　the　sustainable　utilization　of　ENS　in　eco-friendly　construction　materials.　©　2025　The　Authors