To investigate the mechanism and control methods of transverse cracking in prefabricated T-shaped concrete beams caused by frost heave in seasonal frozen soil in alpine-cold mountainous regions, a refined three-dimensional model was established using Diana finite element software to analyze the damage and cracking in the beam body and pedestal concrete of prefabricated beams. The results indicate that frost heave force under low-temperature conditions in alpine-cold mountainous regions is the primary cause of transverse cracking in prefabricated beam bodies. During the frost heave process, a vertical displacement of 39.78 mm occurs in the beam body, with cracks initially appearing at the footing of the expanded foundation of the pedestal. Subsequently, numerous coarse cracks emerge on the surface of the pedestal foundation concrete, and cracks appear in the pedestal concrete slab. Finally, multiple transverse cracks develop in the prefabricated beam body, with the most severe crack measuring 0.3 mm in width and 0.82 m in length. Partial damage is also observed in the pedestal concrete slab. Based on the causes of these transverse cracks, preventive and remedial measures are proposed.