Affected by the cold and high-altitude climate environment, the slope rock body undergoes repeated cycle of freezing and thawing, and the deterioration of physical-mechanical performances may lead to collapse disasters. Relying on the approach road slope of a hydropower station in the western region, the physical model of three typical collapse failure modes of dumping, slipping and falling was studied, aiming to clarify the freeze thawing catastrophe mechanism of high and steep rock slope in the alpine region. The results show that: 1) The temp change rate of fractured rock body is different at different buried depths, and the temp change rate is faster at the position closer to the surface, and the slower the temp change rate at the farther position; 2) After the temp change in the fracture to 0 ℃, the temperature curve showed a temperature plateau, and the platform segment of the deep position curve of the fracture was longer than that of the superficial position curve. The length of the platform segment is inversely correlated with the temperature gradient of the surrounding environment. 3) When the surface temperature of the rock body drops below 0 ℃, the frost heave force begins to increase, and then rises in a fluctuating manner. When the frost heave force pushes the fracture deformation and opening, the pressure is released and the frost heave force is weakened. As the freezing depth continues to develop, the frost heave force will increase again, and so on repeatedly, the overall trend will fluctuate. 4) The frost heave force in the fracture is positively correlated with the freezing depth and the constraints of the rock body. The research results provide a key mechanical basis for the occurrence of freeze thawing collapse disasters on rock slopes, and are of great significance for guiding slope stability assessment and protection engineering design.