Carrying out a comprehensive assessment of land ecological security at the national park scale has important reference value for optimizing the land use management planning of the Sanjiangyuan National Park and strengthening the construction of ecological networks. Integrate indicators such as grassland degradation index, frozen soil stable distribution, ecosystem service value and landscape ecological fragility into the theoretical framework of "stress-state-response" (PSR), analyze the land ecological security status of the Sanjiangyuan National Park and its leading factors are analyzed. The results show that:(1) The overall ecological vulnerability of the Sanjiangyuan National Park landscape is relatively low. The landscape ecological vulnerability index of different parks is slightly different. The vulnerability of the Yangtze River Source Park and the Yellow River Source Park are both moderately vulnerable areas. The landscape ecological vulnerability of the Lancang River Source Park is better than that of the Yangtze River Source Park and the Yellow River Source Park. (2) There are regional differences in the composition and structure of the land ecological security of the Sanjiangyuan National Park, and the overall land ecological security status of the Sanjiangyuan National Park is relatively unsafe. The Yangtze River Source Park and Lancang River Source Park are dominated by less safe zone levels and critical safety levels. The remaining land ecological security levels are distributed in a small number. About 93.94% of the Yellow River Source Park has a safety level of criticality safety and above. (3) The land ecological security layer and relative security layer of the Sanjiangyuan National Park are nested in the central and southern part of the Yangtze River Source Park, as well as the marginal areas on the north and south sides of the Yellow River Source Park. In the Yangtze River Source Park, the Lancang River Source Park and the Yellow River Source Park, the less safe areas and critically safe areas are often staggered across large areas. (4) The identification results of influencing factors based on the GeoDetector model show that settlement density, water network density, and landscape ecological vulnerability are the dominant factors affecting the land ecological security of the Sanjiangyuan National Park. It reveals the comprehensive effect of the degree of disturbance of human activities and the fragility of ecosystems on the ecological security of national parks.