Abstract: The failure of high-positioned rock slope often occurs in alpine and gorge regions of southwest China, resulting in huge casualties and economic and property losses. At present, there are many research theories and physical models for rock landslides, but these theories and models ignore the structural characteristics of rock mass. However, for rockslides, the structural characteristics of rock mass not only control the failure mode of slope deformation, but also affect the fragmentation process of landslide after failure, and even the final hazard range. In this study the discrete element numerical simulation method is used to simulate the fragmentation process of rockslides under different strength of joint, densities of joint, directions of joint and strength of rock mass, and to examine the influence law and mechanism of joint and rock mass characteristics on rockslides fragment characteristics, propagation type and runout. The results show that (1) the horizontal runout of the center of mass increases with the increasing strength of the structural plane, the tensile strength of the structural plane increases by 10 times, and the horizontal runout of the center of mass increases by 3%. (2) The increase of the joint density increases the relative breakage ratio of blocks, but the runout and accumulation area show a downward trend. (3) Compared with other conditions, the runout of mass in the thin bedded rock sheared by the horizontal joint is reduced by about 10%, and the accumulation area is reduced by nearly 30%. (4) The block strength increases, the relative breakage ratio of blocks decreases, and the accumulation area is eventually reduced by 40%. When the block is intact, the runout eventually increases by about 15%. This research is helpful to further understand the fragmentation process of rock landslides and guide disaster prevention and mitigation in mountainous areas.