To　efficiently　and　environmentally　utilize　industrial　waste　nickel　slag　and　enhance　the　high-temperature　performance　of　construction　materials,　this　study　prepared　a　binary　geopolymer　using　nickel　slag　and　blast　furnace　slag　as　raw　materials.　By　leveraging　the　advantages　of　both　materials　and　adjusting　the　ratio　between　nickel　slag　and　blast　furnace　slag,　the　thermal　stability　of　the　geopolymer　at　high　temperatures　was　improved.　This　study　examined　the　mechanical　properties,　mass　loss,　and　thermal　deformation　behavior　of　the　geopolymer　under　high-temperature　exposure.　X-ray　diffraction　(XRD)　and　thermogravimetric　analysis　(TGA)　were　employed　to　examine　the　decomposition　and　phase　transformation　of　the　geopolymer　at　elevated　temperatures.　Mercury　intrusion　porosimetry　(MIP)　and　scanning　electron　microscopy　(SEM)　were　used　to　characterize　the　pore　structure　and　microstructure　after　exposure　to　various　high　temperatures.　The　results　revealed　that　the　formation　of　novel　phases,　including　diopside,　forsterite,　and　spinel,　significantly　enhances　the　thermal　stability　of　the　geopolymer　incorporating　nickel　slag.　Additionally,　the　C-(A)-S-H　gel　formed　during　slag　hydration　fills　the　pores,　improving　the　matrix　density.　This　contributes　positively　to　the　high-temperature　resistance　of　geopolymers　with　high　slag　content.　Overall,　with　a　blending　ratio　of　20　%　nickel　slag　and　80　%　blast　furnace　slag,　the　geopolymer　achieved　a　compressive　strength　of　59.7　MPa　at　28　days.　Under　high-temperature　conditions　of　200,　400,　600,　and　800°C,　the　compressive　strength　retention　of　the　geopolymer　increased　by　11.5　%,　24.8　%,　10.8　%,　and　5.8　%,　respectively,　compared　to　the　pure　blast　furnace　slag　system.　Additionally,　mass　loss　was　reduced　by　1.01　%,　0.81　%,　0.73　%,　and　0.7　%,　and　thermal　shrinkage　at　800°C　was　reduced　by　3.07　%.　Given　its　superior　high-temperature　resistance,　the　nickel　slag-slag　based　binary　geopolymers　holds　promise　as　a　new　type　of　green　building　material　suitable　for　high-temperature　environments.　©　2025