To study the characteristics of secondary collapse disasters along the highway after the Lushan Ms_6.1 earthquake in 2022, taking the section from Lianghekou to Dengchigou of G351 in Baoxing County as an example, through field investigation, statistical analysis and kinematic simulation, the distribution law of hazard-inducing factors and the mechanism of dangerous rock-collapse-rockfall were studied. The results show that the distribution of dangerous rock in the study area is 69.69% in the section of 30m~400 m from the height difference of the highway, 66.66 % in the slope of 60°~90°, 33.33% in the limestone stratum, 78.78% in the distance of 200m~500m from the fault plane, 69.69% in the development of extroversion structural plane, and 69.70% in the particle size of 0.2m~2m. The dangerous rock in the study area is controlled by the combined cutting of structural plane and extroversion structural plane. The slope height is enlarged and the fracture is loosened. The time and space overlap of rainfall and high temperature makes the dry and wet cycle aggravate the damage of structural plane. Rainfall-induced collapse disaster can be divided into four stages: wetting and weight gain of rock and soil on slope surface, water-induced deterioration of structural plane, damage of unstable rock base and triggering of collapse disaster. The stability evaluation formula of unstable rock in limestone stratum considering water-induced deterioration effect of structural plane is established. The kinematic simulation reproduces the trough effect of rockfall disaster. The degree of surface undulation affects the impact energy, motion speed and bounce height in the rockfall movement. It is suggested that the highway in the study area should preferably pass through the rockfall disaster area. The research results provide a reference for the prevention and control of secondary collapse disasters after earthquake in mountain highway slopes.