Abstract: Two large landslide-debris avalanches occurred in Jinsha River at the junction of Baige Village, Bolo Township, Jiangda County, Tibet and Sichuan Province in October and November 2018, respectively. The volumes of the two landslides were about 2400×10⁴ m³ and 850×10⁴ m³, respectively. The two landslides moved down an average distance of 1400 m, blocked the Jinsha River and formed a barrier lake. The first natural outburst of the dam caused no casualties. However, the second landslide blocked the natural crater of the first landslide and resulted in a rapid increase in the storage capacity of the barrier lake to 3.85×10⁸ m³. The government immediately carried out emergency measures to discharge floods by building spillways, which greatly reduced the risk of flood. In this article, a particle flow code in three dimensions(PFC^3D) is adopted to simulate the occurrence, movement and accumulation of the two landslides. Based on the inversion results, we predict the movement path and accumulation scope of the potential dangerous sliding mass in Baige landslide, as well as evaluate its risk scientifically. The results show the follows. (1) Under gravity, in addition to being affected by the initial potential energy, the micro-geomorphology of the landslide is also one of the key factors determining the movement path and the distance of the particles. (2) The PFC^3D particle flow numerical simulation method is suitable for landslides similar to the debris avalanche type such as Baige landslide, and the accumulation scope and thickness obtained from the two simulated landslides are basically consistent with these of the reality. (3) Using the parameters obtained from the inversion of the two events, we predict the instability process of the potentially unstable part of the source area. The unstable slope bodies can collapse and form a barrier dam with a thickness of about 70 m at the Jinsha River, which is possible to block the river again.