The Longmenshan fault zone represents the tectonic boundary between the Tibetan Plateau and the Sichuan Basin. The rapid uplift and geomorphic evolution of its southern segment since the Late Cenozoic are of critical significance for revealing the expansion mechanism of the eastern margin of the plateau. This study aims to quantitatively assess the spatial differentiation of tectonic activity in the southern segment of the Longmenshan fault zone and to explore its controlling effects on the geomorphic development of the upper Qingyijiang River basin.Methods: Based on high- resolution DEM data, four tributaries in the upper Qingyijiang River basin were selected as study objects. Using the ArcGIS 10. 8 platform, five geomorphic parameters were extracted, including the stream length- gradient index (SL), hypsometric integral (HI), the asymmetry factor (AF), valley floor width- height ratio (VF), and circularity ratio (Rc). Combined with Hack profile analysis, a comprehensive geomorphic index was constructed to quantitatively compare tectonic activity.Results: The results indicate that: ① high- value geomorphic parameters (Iat > 2) are mainly distributed near the Gengda—Longdong, Yanjing—Wulong, and Shuangshi—Dachuan fault zones, consistent with the fault trends, reflecting that tectonic activity is the dominant factor controlling regional geomorphic variation; ② The four tributaries exhibit significant variations in tectonic activity: the Tianquan River and Baoxing River basins, controlled by multiple fault zones, demonstrate the highest level of tectonic activity, followed by the Yuxi River, while the Yingjing River shows the weakest activity. Overall, fault zone activity in the region displays a pattern of stronger intensity in the north and weaker in the south; ③ Regional geomorphic evolution results from the multiscale coupling of tectonics, lithology, and climate.Conclusion:These findings revealed how surface processes respond to tectonic deformation on the eastern margin of the Tibetan Plateau, providing new evidence and insights for studying regional tectonic geomorphology evolution.