With the development of social economy and the adjustment of environmental policies, the ecological environment in the arid areas of Northwest China has undergone profound changes since the western regions development policies. This paper selects soil, topography, climate and night lighting data to construct ecological vulnerability assessment indicators based on the ecological background characteristics of the arid areas of Northwest China, which was analyzed the spatio-temporal evolution and motivation of ecological vulnerability by Spatial Principal Component Analysis (SPCA) and geographic detector in 2000, 2007, 2012, and 2018. The results showed that (1) from the spatio-temporal evolution of ecological vulnerability, the research area was mainly dominated by heavy vulnerability. Over the past 18 years, the ecological vulnerability of the study area has remained unchanged. From the perspective of different vulnerability of land use types, grassland and woodland are the slight vulnerability, grassland is the light vulnerability, and unused land is the moderate vulnerability and heavy vulnerability. (2) The dominant factors affecting ecological vulnerability differentiation include soil organic matter content, topographic level index, temperature, precipitation and night light index. Their average power determinant values to ecological vulnerability differentiation are 0.63, 0.36, 0.27, 0.26 and 0.22. (3) Based on the monitoring results of ecological vulnerability and analysis of driving factors, we divide the arid areas of Northwest China into five ecologically functional zones:coreareas of ecological protection, ecological comprehensive concern areas, ecological optimal-concern areas, ecological restoration management areas, and ecological potential management areas. The corresponding management plans are proposed. This study can provide reference for ecological environmental protection in arid areas.