In　order　to　solve　such　as　difficulties　in　backfilling　narrow　foundation　trenches　in　engineering,　it　was　proposed　to　use　alkali-activated　slag　cement　(AASC)　instead　of　traditional　Portland　cement　to　solidify　silt　and　form　AASC　fluidized　solidified　soil.　The　effect　of　the　content　of　AASC　and　the　curing　period　on　fluidized　solidified　soil　has　been　studied　by　unconfined　compression　strength　test,　SEM　and　EDS.　Moreover,　the　root　cause　for　the　improvement　of　the　strength　by　the　microstructure　was　explored.　The　results　showed　that:　The　fluidity　increased　first　and　then　decreased　with　the　increase　of　the　content　of　AASC;　40%　was　the　optimal　content;　in　the　same　curing　period,　the　unconfined　compression　strength　increased　with　the　increase　of　the　content;　40%　was　the　optimal　content;　the　soil　with　different　contents　could　reach　the　most　of　the　28d　strength　on　Day　7;　AASC　generated　a　lot　of　low-Ca/Si　C-S-H　gel　that　consolidated　soil　particles　into　a　denser　structure.　These　results　provide　a　theoretical　basis　for　the　application　of　AASC　in　fluidized　solidified　soil　engineering.