Abstract: Under the impact of climate change, significant changes have taken place in the ecological environment and water cycle of the Yangtze River source area. Soil water is an important component of the hydrological cycle, and a correct understanding of the spatial and temporal distribution patterns and environmental response mechanisms of soil water is the basis for a deeper understanding of the hydrological cycle and ecological environment changes in the Yangtze River source area. It is also of great significance for promoting the sustainable development of the Yangtze River source area. In this paper, based on ground in-situ observation data, combined with the latest long time-series and multi-sensor combined global soil moisture dataset developed by the European Space Agency (ESA CCI SM V07.1), the spatial and temporal evolution of surface soil water in the Yangtze River source area is revealed, and the impact mechanism of structural function and permafrost type on soil water is discussed. The results show that the surface soil moisture in the Yangtze River source area is mainly concentrated between 0.15 and 0.20 m³/m³, with the highest value occurring from June to October. In the vertical direction, the soil moisture content mainly shows an increasing-decreasing-stable trend from the surface to the deep soil layer, and the deep soil water has a significant lag characteristic relative to the surface, with a lag time of generally 1−2 months. In the horizontal direction, the surface soil moisture overall shows a southeast high and northwest gradually decreasing trend. The closer to the structural fault zone, the lower the soil moisture content, and with the increasing depth, it shows a certain aggravating trend. The surface soil moisture content in the permafrost area is higher than that in the neighboring seasonal frozen soil area. The fluctuation range of the surface soil moisture content in the seasonal frozen soil area is smaller than that in the permafrost area. Over the past 40 years, the surface permafrost has shown a trend of gradual melting, and since 2000, the melting of permafrost has intensified, with a significant increase in surface soil moisture content. The results of this study are of great theoretical significance for the in-depth understanding of the hydrological cycle and ecological environment changes in the Yangtze River source area, and can provide a reference basis for the hydrological cycle and water resources management in the Yangtze River source area.