The evolution of collision-fragmentation-disintegration has a significant control effect on the motional characteristics of large-scale high-speed rockslides, and affects the geological structure characteristics and the stability of accumulation body. This paper takes Tangjiashan high-speed rockslide as research object. It relies on the geological analysis principle. It interprets the fragmentation process and characteristics of collided sliding body. It further carries out the falling-collision experiments of cylindrical rock blocks drilled from the deposits. The weight loss induced by collision is quantified and the grading size of fragments is analyzed. In term of observation, it is shown that the higher the impacting velocities, the more mass loss, the finer the fragments tend to be, of which the friction coefficient is usually lower than the initial intact rocks. Moreover, the conventional mechanics experiment of impacted rock before and after collision is carried out to obtain the correlation between the impacting velocity and the mechanical parameters of rock blocks. The result shows that collision could greatly reduce the mechanical indexes of rock masses. Considering the macroscopic condition, the physical collision model experiment along a designed channel is implemented to acquire the relationship between the velocity and pattern of collision and the runout of landslide, as well as the accumulation form. The conclusion could provide some reference for the scope prediction of high-speed rockslide.