Abstract: Qinghai Lake is the largest endorheic lake on the Qinghai-Tibet Plateau. Research on the hydrological regime changes of Qinghai Lake holds great significance for regional water resource management and ecological environment protection. This study comprehensively utilized multi-source remote sensing images, satellite altimetry data, and hydro-meteorological data to explore the variation trends of Qinghai Lake's area, water level, and water volume from 2003 to 2023, and quantitatively analyze the contribution of each component to the water balance of Qinghai Lake. The results showed that: from 2003 to 2023, the increasing trends of Qinghai Lake's area, water level, and water volume were 18.65 km²/a, 0.20 m/a, and 0.91 km³/a respectively, which can be roughly divided into three stages of stable expansion, rapid expansion, and slow expansion; among the water balance components, the contribution rates of terrestrial precipitation runoff, lake surface precipitation, permafrost meltwater, and glacial meltwater to the total inflow water volume were 57.2%, 41.6%, 0.8%, and 0.4% respectively. Among these, the increase in terrestrial precipitation runoff and lake surface precipitation were the dominant factors leading to the changes in the hydrological regime of Qinghai Lake.