[Objective] The study aims to explore the impact of future climate and land use changes on runoff prediction and its influencing mechanisms in lake basins, which helps to understand hydrological response patterns, optimize water resource allocation, and formulate adaptive management strategies. [Methods] Taking the Erhai Lake Basin as the study area, the research integrates CMIP6 climate data and land use data, coupling the PLUS model and SWAT model to construct a framework for predicting runoff under future climate and land use change scenarios. This framework predicts runoff in the Erhai Lake Basin based on three climate scenarios (SSP1-1.9, SSP2-4.5, and SSP5-8.5) under different Shared Socioeconomic Pathways (SSPs) and future land use change scenarios. The optimal parameter geographical detector is used to reveal the main driving factors and their interactions affecting runoff in the Erhai Lake Basin. [Results] 1) Cultivated land, forest land, and grassland are the dominant land use types in the Erhai Lake Basin over the long term. From 2010 to 2020, urbanization drove the expansion of construction land, encroaching on cultivated land and forest land. By 2030, construction land is expected to reach 18396 hm2, with an additional 1427 hm2 of new construction land, mainly converted from cultivated land, reflecting pressures from population growth and infrastructure demands. 2) The runoff in the Erhai Lake Basin in 2030 shows certain variations under the three scenarios. The highest runoff is observed under the SSP5-8.5 scenario (19.592 m3/s), followed by the SSP1-1.9 scenario (18.013 m3/s), and the lowest under the SSP2-4.5 scenario (17.387 m3/s). Despite variations under different emission scenarios, the overall trend remains relatively stable. 3) The geographical detector results indicate that wind speed exhibits strong independent explanatory power in most years, while the combination of precipitation and other factors shows highly significant interactive explanatory power across all years. [Conclusion] The runoff in the Erhai Lake Basin in 2030 remains relatively stable across different scenarios, with the annual average runoff following the trend of SSP5-8.5 > SSP1-1.9 > SSP2-4.5. Wind speed has the greatest impact on runoff under all three scenarios in 2030, while the combination of precipitation and other factors outperforms other combinations in influencing runoff.