［Objective］The relationship between annual runoff and sediment load in the Upper Yangtze River basin （UYRB）had a significant change under the operation of large reservoirs. There was no obvious variation in the annual runoff processes in the UYRB，while the annual sediment load decreased greatly.［Methods］Based on the annual runoff and sediment load observation series in the mainstream and main tributaries in the UYRB during 1950—2022，improved double mass curve method was utilized to calculate the deviation sequences of the double mass curves and introduce the scaling factors，thereby analyzing the cumulative mutation characteristics of the relationship between annual runoff and sediment load.［Results］The relationship between annual runoff and sediment load in the UYRB had significantly changed in 1985，1998，2002 and 2013，respectively. As a result， the average sediment content in the UYRB decreased from 1.20 kg/m³ to 1.02，0.77，0.12，0.03 kg/m³， respectively. Combined with the distribution of large reservoirs in the river network，the four mutations in the relationship between annual runoff and sediment load in the UYRB were caused by the operation of Baozhusi Reservoir and Wujiangdu Hydropower Station，Ertan Reservoir，Three Gorges Dam，Xiangjiaba and Xiluodu Reservoir. Operation of large reservoirs led to a reduction of annual sediment load by 515 million tons in the upstream，with a 97.17% sediment reduction rate in the upstream.［Conclusion］Improved double mass curve method can effectively quantify the cumulative change in the relationship between runoff and sediment load and identify mutation points across multiple temporal scales. The mutations in the relationship between annual runoff and sediment load in the UYRB were predominantly driven by sediment interception from reservoir groups，while the spatiotemporal superposition effects of reservoirs in both tributaries and the mainstream further intensified the cumulative variations. The research findings can provide a theoretical basis for regulation of runoff and sediment load in the basin.