<p>The high-position landslide disasters are frequent in Qinghai-Tibet Plateau, which is susceptible to the river blockage induced by the reactivated ancient landslides. However, accurately assessing these characteristics in high-position ancient landslides presents significant challenges due to the limited comprehensive investigations in the mountainous terrains in plateau. The risk assessment process for high-position landslides in plateau mountainous area is proposed in this study. The movement dynamics of the Peilong ancient landslide, located in the southeastern Tibetan Plateau, is analyzed as an example of high-position ancient landslides. The assessment is conducted by the integration of Interferometric Synthetic Aperture Radar (InSAR) with unmanned aerial vehicle (UAV) surveys and extensive field investigations. It explores the rapid runout behavior of landslides under conditions of severe earthquakes and heavy rainfall. The results from the temporal monitoring by InSAR technique indicates that rainfall is the primary trigger of displacement development of Peilong ancient landslide, rather than snowmelt infiltration due to rising temperatures. And landslide displacements occur with a lag behind rainfall. The likelihood of river obstruction is closely related to the trajectory of the landslide debris, with an elevated risk of blockage occurring near river channels. Additionally, terraces with gentle inclines are identified as critical areas susceptible to blockage in V-shaped river channels, while the central and adjacent regions of U-shaped channels are primary zones at risk. These findings enhance our understanding of the movement patterns of slow-moving, high-position ancient landslides, highlighting critical zones for targeted river blockage mitigation in mountainous landscapes.</p>