Abstract: The balance of ecological conservation and coordinated community development is a fundamental objective in the construction of the Sanjiangyuan National Park. Facing ongoing climate change and accelerating urbanization, the evolution of human settlements in the Sanjiangyuan Region has garnered considerable attention. This study established an assessment index system for human settlement quality tailored to the region′s characteristics from the perspective of human-environment relationships and systematically evaluated the spatiotemporal dynamics of human settlement quality in the Sanjiangyuan Region between 2000 and 2024. The principal findings are as follows. (1) From 2000 to 2024, the overall human settlement quality in the Sanjiangyuan Region exhibited a marked upward trend, with continuous improvement observed across the region. Influenced by factors such as the region′s vast expanse and low population density, the spatial heterogeneity of human settlement quality was pronounced, and its spatial distribution pattern closely mirrored that of population density. The human settlement index for urban areas (0.467±0.042) was significantly higher than those for rural areas (0.443±0.031) and pastoral areas (0.363±0.029). Substantial disparities in improvement rates were evident among urban, rural, and pastoral settings. Urban areas demonstrated the fastest rate of increase, rising by approximately 0.058/10 a, notably faster than rural areas (0.043/10 a) and pastoral areas (0.038/10 a). Over the 25-year period, the human settlement index across the 22 counties and cities within the Sanjiangyuan Region displayed two distinct development phases. Prior to 2016, most counties and cities experienced steady improvement in human settlement conditions. After 2016, the development of human settlements entered a phase of accelerated enhancement. Tongren City (Huangnan Tibetan Autonomous Prefecture) recorded the highest human settlement index, while Golmud City (Tangula Mountain Town) registered the lowest. (2) The overall human settlement quality in the Sanjiangyuan Region exhibited a spatial gradient pattern, progressively increasing from the southwest to the northeast. Areas suitable for human habitation were predominantly concentrated in the built-up areas of county seats in the northeastern part, while the vast central and southwestern expanses, represented by Zaduo County, largely remained unsuitable for settlement. (3) Over the 25-year period, improvements in human settlement quality across the Sanjiangyuan Region were primarily driven by socioeconomic development, which contributed an average of 59.77% to the observed enhancements. Economic development served as the core driving force, with social environmental factors (15.16%) providing substantial support. This study establishes a human settlement evaluation framework applicable to ecologically fragile high-altitude regions and offers a comprehensive assessment of human settlement quality in the Sanjiangyuan Region. It furnishes a scientific foundation for regional ecological conservation, urban development, and the enhancement of living environments, while advancing the coordinated and mutually beneficial pursuit of ecological conservation, green development, and livelihood improvement within the Sanjiangyuan National Park.