<p>Freeze–thaw (F–T) cycles alter rock pore structure and promote cracking in cold regions. Understanding how pore-structure changes drive crack propagation is critical for addressing stability problems in cold-region rock engineering. This study investigates the evolution of pore-structure connectivity in water-saturated weathered granite during F–T cycling and its influence on crack propagation, providing insights essential for improving the safety and durability of rock engineering projects in cold environments. Nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and acoustic emission (AE) monitoring were used to characterize pore-structure evolution, crack development, and their interrelationship. The results show that increasing F–T cycles progressively reduced peak strength and elastic modulus. When porosity increased by 70.37%, peak strength and elastic modulus decreased by 45.02% and 51.03%, respectively. AE results show that low-porosity specimens had fewer burst-type high-energy events, which are linked to abrupt brittle failure. In contrast, high-porosity specimens produced many low-energy events from progressive crack growth, along with occasional high-energy events caused by unstable crack coalescence. The pore-connectivity index, calculated from pore-size and pore-throat data, indicates that F–T cycling increases pore connectivity. This promotes local stress concentration and microcrack propagation. Combined SEM–AE analysis reveals that damage evolved from early activation of pre-existing defects to a later damage pattern dominated by large cracks. Overall, crack evolution shifted from enhanced microcrack initiation to intensified crack propagation and coalescence. These findings demonstrate that F–T cycling regulates crack propagation by modifying pore connectivity and provide theoretical insight and technical support for understanding F–T-induced pore-structure degradation in cold-region rock engineering.</p>