Abstract: The Taoyuan paleolake is located at the main stream of the Jinsha River, on the southeastern edge of the Qinghai-Tibet Plateau, a region characterized by intense tectonic activity. This complex geological setting is highly prone to trigger a cascade of geological disasters, including earthquakes, landslides, and dammed lakes. To further analyze the causes of landslide-induced dammed lakes on the Jinsha River’s mainstream, this study utilized 30 m resolution DEM data and ArcGIS spatial analysis technology. This allowed for the extraction of tectonic geomorphological indices along the Jinsha River’s main stream at Taoyuan paleolake and its adjacent areas, including slope, relief degree of land surface, hypsometric integral, and river steepness index. These indices were compared with non-structural factors (precipitation and lithology) to discover significant differences in tectonic geomorphology between the upstream lacustrine sedimentary areas and downstream areas of the Jinsha River, with the Zhaizicun ancient landslide serving as a dividing point. In addition, combined with the analysis of previous research findings, it further confirmed that the tectonic activity of the Chenghai fault is the primary factor influencing the formation of the Zhaizicun ancient landslide and the differences in tectonic geomorphology in the surrounding areas. The blockage of the river caused by the landslide is also the main reason for the formation of Taoyuan paleolake. This indirectly reflects that regions with abnormal changes in tectonic geomorphology along rivers are prone to form landslides.