[Objective] The study aims to explore the impact of future climate and land use changes on runoff prediction and its influencing mechanisms in a lake basin. It helps investigate hydrological response patterns， optimize water resource allocation，and formulate adaptive management strategies. [Methods] Taking the Erhai Lake Basin as the study area，the research integrated CMIP6 climate data and land use data，coupling the PLUS model and SWAT model to construct an analytical framework for runoff prediction under future climate and land use change scenarios. This framework predicted runoff in the Erhai Lake Basin under three climate scenarios based on Shared Socioeconomic Pathways（SSP1-1.9，SSP2-4.5，and SSP5-8.5），combined with future land use change. The geodetector with optimal parameter was used to reveal the main driving factors and their interactions affecting runoff in the basin. [Results] 1）Cultivated land，forest land，and grassland were 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，taking over cultivated land and forest land. By 2030，construction land was expected to reach 18 396 hm²，with an increase of 1 427 hm² mainly converted from cultivated land，reflecting the pressures of population growth and infrastructure demand. 2）The runoff in the Erhai Lake Basin in 2030 showed variations under the three scenarios. The highest runoff was 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 remained relatively stable. 3）The geodetector results indicated that wind speed exhibited strong independent explanatory power in most years，while the combination of precipitation and other factors showed significant interactive explanatory power. [Conclusion] In 2030，runoff in the Erhai Lake Basin remains relatively stable under all scenarios，with the annual average runoff following the trend of SSP5-8.5>SSP1-1.9>SSP2-4.5. In all three scenarios for 2030，wind speed has the greatest impact on runoff in the Erhai Lake Basin，while the combination of precipitation and other factors has a greater influence on runoff than other combinations.