The　efflorescence　problem　is　always　an　intractable　problem　for　geopolymer.　Silica　fume　(SF),　nano-silica　(NS),　5A　zeolite　(ZL)　and　nano-silica　treated　with　silane　(NST),　were　used　to　mitigate　the　efflorescence　of　fly　ash　(FA)　-　granulated　blast　furnace　slag　(GBFS)　-　steel　slag　(SS)　based　geopolymer.　The　effect　of　their　dosages　on　the　efflorescence　was　evaluated　through　accelerated　efflorescing,　leaching　and　unconfined　compressive　strength　(UCS)　tests.　The　inhibition　mechanisms　were　explored　by　XRD,　SEM,　FTIR　and　MIP　characterization.　It　revealed　that　SF　and　NS　presented　the　most　effective　mitigating　effect　on　efflorescence,　with　9　%　of　SF　and　2　%　of　NS　totally　inhibiting　efflorescence　and　improving　the　compressive　strength,　and　ZL　and　NST　also　alleviated　the　efflorescence　at　appropriate　contents.　Optimizing　pore　network　and　stabilizing　free　alkali　were　found　to　be　the　most　important　aspects　for　inhibiting　efflorescence.　The　SF　and　NS　worked　efficiently　in　both　two　ways,　which　contained　a　large　amount　of　dissolvable　silicate　that　reacted　with　the　excessive　alkali　to　form　C(N)-A-S-H　and　C-S-H　gels.　This　filled　and　reduced　the　pores　from　26　nm　to　less　than　10　nm,　and　stabilized　alkali　with　reduce　the　free　w(Na+)　by　more　than　50.45　%.　On　the　other　hand,　ZL　can　solidify　free　alkali　through　the　ion　exchange　property　and　fill　pores　due　to　its　microaggregate　nature,　and　NST　reduced　the　efflorescence　through　blocking　free　alkali　migration　paths　by　hydrophobicity　of　the　pores.　These　findings　would　guide　the　selection　of　appropriate　methods　to　solve　the　efflorescence　problem　of　geopolymers.　©　2024　Elsevier　Ltd　and　Techna　Group　S.r.l.