Objective The Dadu River Basin is an important ecological barrier between the upper reaches of the Yangtze River and the eastern foothill of the Qinghai-Tibet Plateau. It is of great theoretical and practical significance to study regional ecological vulnerability for environmental protection in the river basin.

Methods This paper selected 14 evaluation indexes by SRP model and constructed the Dadu River basin ecological vulnerability assessment system by AHP.

Results ① The classification of ecological vulnerability from high to low is extremely severe fragility (EVI≥0.50), severe fragility (0.46≤EVI < 0.50), moderate fragility (0.42≤EVI < 0.46), mild fragility (0.38≤EVI < 0.42), and slight fragility (EVI < 0.38). (2) The northern and central parts of the basin are mostly extremely severe fragility and severely fragility areas, and the ecological vulnerability index decreases with altitude. (3) In terms of spatial-temporal transformation, the area of slight vulnerability decreased by 2033 km², which accounted for 2.74% of the total watershed area. Extremely severe fragility areas increased by 2,649 km², or 3.41 percent. (4)From the perspective of factor detection, the factors with the strongest explanatory power for ecological vulnerability are GDP, population, annual sunshine, soil viscosity and annual average relative humidity. In terms of interactive detection, there is a strong interaction among all factors, and ecological vulnerability is the result of the comprehensive effect of all factors. (5) From the perspective of origin, the extremely severe fragility and severe fragility areas are mostly located in the plateau and mountain, and climate and topography are the important reasons for their ecological fragility. Human economic activities are closely related to the degree of vulnerability.