In　response　to　the　high　carbon　emissions　from　cement　production,　carbon　mineralization　for　CO2　sequestration　and　alternative　cementitious　materials　have　gained　attention.　However,　carbon　mineralization　faces　equipment　and　energy　challenges,　while　geopolymer　materials　suffer　from　poor　workability.　This　study　proposes　a　novel　method　combining　mechanochemical　activation　and　dry　ice　(solid　CO2)　and　explores　its　effects　on　the　behavior　of　slag　based　geopolymer　(SBG)　mortar.　This　study　demonstrates　that,　compared　to　the　individual　addition　of　dry　ice　or　mechanical　activation　alone,　using　dry　ice　as　a　grinding　medium　allows　it　to　embed　into　the　particle　structure　in　the　form　of　distorted　carbonates.　The　mechanochemical　process　continuously　disrupts　the　carbonate　layer,　exposing　fresh　unreacted　surfaces,　thereby　promoting　ongoing　reactions　and　significantly　enhancing　the　carbon　sequestration　efficiency　of　SBG.　While　the　addition　of　dry　ice　delays　early　hydration　reactions,　it　promotes　the　generation　of　increasing　hydration　and　carbonation　products　in　the　mid　to　late　stages,　enhancing　the　mortar＇s　density　and　strength.　Specifically,　at　a　dry　ice　content　of　2.7　%　with　mechanochemical　processes,　the　comprehensive　performance　of　SBG　mortar　is　optimal　after　mechanochemical　mixing,　exhibiting　moderate　workability　(214　mm　fluidity),　high　compressive　strength　(54.8　MPa　at　28d),　low　drying　shrinkage　(623　mu　epsilon　at　28d),　and　strong　resistance　to　chloride　ion　penetration　(1884.18　C　electrical　flux).