Abstract: To address the insufficient understanding of centennial-scale water—sediment evolutionary characteristics in the Yellow River Basin and the ambiguous identification of driving mechanisms across different temporal scales, the drainage area upstream of the Huayuankou Station is taken as the research object in this study. Based on monthly runoff, sediment transport and climatic datasets from 1919 to 2022, a multi-scale attribution framework coupling the Budyko hydrothermal balance principle and fractal elasticity theory is constructed. The analysis results show that over the centennial timescale, the annual precipitation in the Yellow River Basin exhibits a statistically significant increasing trend (0.31mm/a, p<0.01), while both runoff and sediment transport decrease markedly (−2.35×10⁸m³/a and −0.16×10⁸t/a, p<0.01), with the water—sediment coupled system exhibiting prominent non-stationary properties. Water and sediment evolution feature notable multi-scale asynchronous variations: decadal changes differ greatly in timing, amplitude, and trajectory; at the intra-annual scale, the seasonal allocation of water and sediment has transformed from a flood-season-concentrated pattern toward a more uniformized annual distribution since 2000. Human activities act as the predominant driver of water—sediment variations at the centennial scale, contributing 73.2% to runoff reduction and 81.4% to sediment transport reduction, and the magnitude of sediment reduction outweighs the runoff reduction. Attribution results display clear temporal scale dependence: human interference dominates water—sediment changes during flood seasons and periods with intensive human activities, while climate change exerts a relatively predominant effect in non-flood seasons and certain decadal transition stages. In general, the centennial water—sediment system of the Yellow River Basin has completed a regime shift, transitioning from an evolutionary stage mainly driven by natural climate fluctuations to a non-stationary evolutionary stage governed by human regulation.