Abstract: Freeze-thaw cycles are critical factors influencing rock landslides in high-altitude mountainous regions. In this study, rock samples from the Lagangcun landslide in a high-altitude area are collected to conduct triaxial unloading tests on fractured conglomerates subjected to varying freeze-thaw cycles. The mechanical properties, energy evolution, acoustic emission characteristics, and multi-scale structural features are systematically analyzed to elucidate the freeze-thaw degradation mechanism of conglomerate with prefabricated fissures. The results demonstrate that the peak strength of the samples progressively decreases with increasing freeze-thaw cycles. After 60 freeze-thaw cycles, compared to untreated samples, the peak strength of intact specimens under confining pressures of 10 MPa, 20 MPa, and 30 MPa decreases by 44%, 48%, and 70%, respectively. Under identical confining pressure and freeze-thaw cycles, samples with longer pre-existing fractures exhibit lower peak strength and greater susceptibility to failure. Both the absorbed and dissipated energies during rock failure decreased with freeze-thaw cycle, indicating that less energy is required to induce failure. As freeze-thaw cycles increase, the average acoustic emission energy per second diminishes, the number of rupture points declines, and the failure duration is shortened. The failure mode transitions from X-shaped shear failure to tensile-shear conjugate failure. At the macroscopic scale, the secondary cracks or fractures are closely associated with pre-existing fissures. Microscopic analysis reveals that crack propagation intensified with freeze-thaw cycles. Compared to untreated samples, 4 cm pre-fractured specimens after 40 and 60 cycles show crack volume increases of 1.71% and 1.83%, respectively, with more pronounced cracking along pre-existing fractures, highlighting the exacerbated damage in fractured rocks. These findings clarify the strength degradation law of conglomerates under freeze-thaw conditions, providing critical insights for engineering construction and rock mass stability in alpine regions.