This study investigates the influence of temperature on the development mechanism of early-age compressive strength in alkali-activated slag (AAS) systems, with a focus on elucidating the structure–property relationships between the formation of microscopic crystalline phases, the growth of gel products, and the macroscopic mechanical performance. The results indicate that the evolution of early strength in AAS proceeds through four distinct stages: an induction period, a slow growth phase, an accelerated growth period, and a steady development stage. As temperature decreases, the strength development of AAS becomes significantly impeded, characterized by a prolonged induction period and extended slow growth phase, while the accelerated growth and steady development stages gradually diminish. At curing temperatures of 0℃ and ?20℃, the 28-day compressive strength of AAS dropped markedly to 16.2?MPa and 3.1?MPa, respectively, representing reductions of 67.5% and 93.8% compared to the reference group cured at 20?℃. Mechanistic analysis reveals that low temperature induces a sharp decline in strength through a triple inhibition mechanism: kinetic arrest of chemical reactions, frost expansion damage caused by pore water freezing, and reduction in reactive interfaces. These factors collectively contribute to sustained suppression of polymerization kinetics, induction of microstructural damage due to ice formation, and a significant decrease in the proportion of available liquid water, thereby fundamentally undermining strength development.