Abstract: This is an article in the field of ceramics and composites. Alkali-activated Slag-fly Ash-based Geopolymer (ASFG) has excellent properties such as high early strength, acid and alkali resistance, but its large brittleness and poor toughness affect its popularization and application. In order to improve the properties of ASFG and broaden the types of mineral admixtures that can be used for ASFG modification, six kinds of mineral admixtures, including metakaolin, zeolite powder, bentonite, wollastonite powder, light calcium carbonate and silica fume, are used as modified materials, and their modification effects on ASFG are studied. The optimum modified material is silica fume. In order to further explore the improvement effect of silica fume on the mechanical properties of ASFG, the effect of the content of silica fume on the mechanical properties of ASFG is studied, and the optimal content of silica fume is determined. Finally, Alkali-activated Slag-fly Ash-silica Fume-based Geopolymer Concrete (ASFSGC) is prepared, and its workability, quasi-static mechanical properties and impermeability are studied. The results show that bentonite, wollastonite powder, light calcium carbonate and silica fume can significantly improve the flexural strength of ASFG. Wollastonite powder and silica fume can significantly improve the compressive strength of ASFG. For ASFG, silica fume is a premium mineral admixture. With the increase of silica fume content, the mechanical properties of ASFG first increase and then decrease, and the optimal content of silica fume is 4%. ASFSGC has good workability and excellent impermeability, and the ductility of ASFSGC is 14.1% larger than that of ordinary Portland cement concrete.