Abstract: Quantifying the relative contributions of climate change and human activities to runoff and sediment variations is essential for understanding hydrological processes in alpine regions. Based on hydro-meteorological data from 1960 to 2021 in the source region of the Yangtze River, this study systematically analyzed the driving mechanisms of runoff and sediment dynamics using the Double Mass Curve, the Slope Changing Ratio of Cumulative Quantity, and the elasticity coefficient method. The results show that: ① A significant warming and wetting trend was observed, with temperature and precipitation at the Zhimenda Station increasing by 0.37 °C/(10a) and 13.58 mm/(10a) (P < 0.01), respectively. ② Spatial heterogeneity was evident: runoff at the Tuotuohe and Zhimenda stations increased significantly, whereas the Xinzhai Station exhibited a concurrent decrease in both runoff and sediment load. ③ Climate change was the dominant driver for increased runoff, while sediment variations were predominantly controlled by human activities at Zhimenda Station. Conversely, the synchronized decrease in runoff and sediment at the Xinzhai Station was primarily driven by human activities. The three attribution analysis methods exhibit high consistency in identifying dominant driving factors, with the elasticity coefficient method exhibiting superior robustness. Multi-method ensemble analysis effectively mitigates the uncertainty inherent in individual approach, providing a more reliable scientific basis for attributing runoff and sediment variations in alpine basins.