To quantitatively assess the contribution rates of climate change and human activities to the changes in runoff and sediment inflow into Poyang Lake, based on the observed runoff and sediment data at hydrological stations of five major tributaries in the Poyang Lake Basin from 1957 to 2023, the trend and abrupt points of runoff and sediment inflow into the lake were analyzed using the Mann-Kendall test and cumulative anomaly method, and the SWAT model was used to simulate water-sediment processes before and after the abrupt points in the basin. The results showed that the annual average runoff inflow into Poyang Lake exhibited an insignificant increasing trend, while the annual average sediment load into the lake demonstrated a statistically significant decreasing trend, with abrupt changes of runoff and sediment occurring in 1990. Compared with the baseline period of 1957-1989, the annual average runoff inflow into the lake from 1990 to 2023 increased by 10.12 billion m³, and the annual average sediment load into the lake decreased by 6.298 million t. Climate change is the primary driving factor leading to the increase in the runoff inflow into Poyang Lake, with a contribution rate of 78.7%, and human activities play a dominant role in reduction of the sediment load into Poyang Lake, with a contribution rate of 85.1%.