To elucidate the inhibition mechanism of low temperatures on the geopolymerization reaction of alkali-activated slag (AAS) at the molecular level, the development mechanism of the compressive strength of AAS under different temperatures was investigated, and the structure-activity relationship between microscopic mineral crystal formation, gel growth behavior, and macroscopic mechanical properties was analyzed. The results indicate that the early-age strength evolution of AAS undergoes four stages: a preparatory stage, a low-speed growth stage, a rapid growth stage, and a plateau development stage. As the ambient temperature decreases, the strength development of AAS is hindered, with the preparatory and low-speed growth stages being prolonged, while the rapid growth and plateau stages gradually disappear. At 0 ℃ and -20 ℃, the 28 d compressive strength of AAS plummeted to 18.6 MPa and 3.1 MPa, respectively, representing dramatic decreases of 72.9% and 95.5% compared to the 20 ℃ reference group. Mechanistic analysis reveals that low temperatures induce a catastrophic decline in strength through three synergistic inhibition pathways: retardation of reaction kinetics, frost heave damage from free water, and reduction of the reaction interface. The sustained suppression of the polymerization kinetics, the induction of microstructural damage from frost heave, and the significant reduction in the proportion of effective liquid water in the system collectively and fundamentally undermine strength development.