Abstract: Based on GIS, evaluation indicators from terrain, meteorology, vegetation, soil, human activities, et al, were selected, spatial principal component analysis was used to quantitatively evaluate the local ecological vulnerability of Yalong river basin, and the spatial pattern characteristics and driving force of ecological vulnerability in 1995, 2005 and 2015 were explored. The results showed that,in terms of time scale, the comprehensive index of ecological vulnerability of Yalong river basin increased gradually, and the overall condition of ecological environment was at a medium level. In the perspective of spatial scale, the ecological vulnerability degree gradually reduced from upstream to downstream. In different altitude gradient zones, the ecological vulnerability degree of the extremely high altitude area （≥4 500 m）and the high altitude area （3 500~4 500 m）was relatively high, while the ecological vulnerability degree of the middle and high altitude area （2 500~3 500 m）, the middle altitude area （1 500~2 500 m） and the low altitude area （<1 500 m）was relatively weak. Owing to the vigorous implementation of ecological environment protection policies by the local government and the enhanced environmental protection awareness of local residents, the ecological environment of 9 counties in the study area improved from 2005.

Key words: ecological vulnerability, principal component analysis, influencing factors, Yalong river basin