Large　autogenous　shrinkage　of　alkali-activated　slag　(AAS)　cementitious　materials　and　the　potential　high　early　cracking　risk　is　a　critical　issue　for　their　practical　application.　This　study　explores　the　use　of　doped　diatomaceous　earth　(DE)　to　mitigate　autogenous　shrinkage　in　AAS　systems.　By　partially　replacing　ground　granulated　blast-furnace　slag　(GGBFS)　with　calcined　DE,　the　research　evaluates　shrinkage　mitigation　across　various　DE　dosages　and　alkali　equivalents.　The　hydration　process　and　the　phase　compositions　of　AAS　with　doped　DE　were　also　experimentally　investigated　via　multiple　microscopic　technique　including　scanning　electron　microscopy　(SEM),　X-ray　diffraction　(XRD),　and　thermogravimetric　analysis　(TGA).　Test　results　show　that　DE　significantly　reduces　autogenous　and　chemical　shrinkage,　with　a　25%　DE　replacement　achieving　reductions　of　53.1%　and　28.4%,　respectively.　The　primary　mechanism　for　shrinkage　suppression　is　attributed　to　DE＇s　relatively　lower　reactivity,　which　induces　dilution　effects,　slowing　the　hydration　reaction　of　GGBFS　and　reducing　the　formation　of　shrinkage-inducing　compounds　like　C–(N)–A–S–H　gel　and　hydrotalcite-like　compounds.　nuclear　magnetic　resonance　(NMR)　analysis　further　reveals　that　DE　increases　the　mean　chain　length　of　C–A–S–H　gel,　hindering　gel　recombination　and　rearrangement　and　contributing　to　reduce　autogenous　shrinkage　by　other　way.　This　work　also　highlights　that　the　shrinkage　mitigation　effect　varies　with　alkalinity　levels,　with　optimal　results　achieved　at　alkali　equivalents　between　5%　and　6%.　Importantly,　DE　dosages　up　to　20%　do　not　compromise　the　workability　or　mechanical　properties　of　AAS　materials.　This　research　demonstrates　that　doped　DE　is　an　effective　technique　for　reducing　autogenous　shrinkage　of　AAS　materials　with　ensured　flowability　and　strength.　©　2025　The　American　Ceramic　Society.