Spray-based air-leakage sealing is a key technology for preventing coal spontaneous combustion in goafs. To overcome the high brittleness and poor durability of traditional cement-based materials, this study developed a novel inorganic sealing system incorporating silica fume, metakaolin, and sodium silicate. The effects of their contents on adhesion, compressive strength, permeability, and self-healing properties were investigated. The optimal performance was achieved with 6% silica fume, 10% metakaolin, and 3% sodium silicate, resulting in an adhesion of 22.63 g and a permeability of 0.48×10?2 mD after 25 days of curing. Self-healing tests revealed that alkali-activated silica fume and metakaolin form a C-S-H/N-A-S-H composite gel, which synergizes with expansive products like ettringite to seal cracks effectively. This work provides theoretical and technical support for designing durable sealing materials in deep mining.