Abstract: The rock bridge in the slope rock mass has a controlling effect on the slope stability. In order to explore the deformation and failure characteristics and crack expansion mechanism of the jointed rock bridge, in this paper, the crack initiation, propagation, penetration and microscopic damage evolution characteristics of rock bridge are analyzed by prefabricating cracks at the end of complete specimen to form middle rock bridge combined with digital image correlation technology. The crack initiation, propagation and penetration mechanism of rock bridge is revealed by using the theory of fracture mechanics. The results show that the fracture process of rock bridge specimen can be divided into five stages and the strain-strain curve shows the characteristics of “pre-peak fluctuation” and “post-peak step” decline. The failure process of the rock bridge specimen is as follows: first, the crack initiation of the lower inclined crack, and then the deflection extends upward at a certain angle, and the crack expansion extends step by step; the failure of rock bridge samples is caused by the accumulation of damage in the early stage. The local high strain region formed at the crack tip indicates the propagation path of macro fracture; the expression of stress intensity factor at the crack tip is derived, and the crack initiation angle is calculated. The theoretical calculation is consistent with the experimental results.