Calcium　carbide　reduce-mirabilite　was　used　as　an　alkaline　activator　to　prepare　geopolymer　materials　based　on　phosphorus　tailings　(PT)　and　blast　furnace　slag　(BFS)　for　immobilization　of　anion　fluorine　(F).　The　influence　of　free　F　on　mechanical　properties,　microstructure,　and　microtopography　of　geopolymers　was　discussed.　The　immobilization　effect　and　mechanism　of　geopolymers　on　free　F　were　studied.　The　results　show　that　free　F　will　cause　more　pores　in　the　geopolymer,　increase　the　proportion　of　unreacted　particles　and　N-A-S-H　gel,　and　reduce　the　proportion　of　C-(A)-S-H　gel,　resulting　in　a　slight　decline　in　mechanical　properties.　The　leaching　test　shows　the　F　leaching　concentration　gradually　decreases　while　immobilization　rate　gradually　increases　with　increasing　BFS　proportion.　The　immobilization　mechanism　of　free　F　is　reflected　in　that　Ca2+　in　geopolymer　reacts　with　free　F　to　form　insoluble　precipitates　CaF2　and　Ca5(PO4)3F,　and　the　further　immobilization　of　free　F　by　the　physical　encapsulation　of　gel　in　geopolymer.