Forests and shrub vegetation，as the main components of the Qilian Mountain forest ecosystem，undertake a variety of ecological functions such as conserving water sources，regulating precipitation and snow and ice in mountainous areas and surrounding areas，irrigating the oasis of the Hexi Corridor，and maintaining biodiversity. The distribution，structure and composition of forest and shrub vegetation in Qilian Mountains have obvious spatial and temporal differentiation rules，and are controlled by water conditions and heat. At the same time，global climate change is also profoundly affecting the temporal and spatial differentiation of forests and shrub vegetation in Qilian Mountains. In view of this，this study comprehensively analyzed the spatial and temporal differentiation of forest and shrub vegetation in Qilian Mountains and its driving changes，indicating that from east to west along the Qilian Mountains，the precipitation decreased，and the distribution areas of Qinghai spruce and Qilian Sabin gradually narrowed. The coverage gradually decreases to the western end of the Qilian Mountains，mainly shrubs；in the vertical distribution along the elevation，the shrub is the highest altitude species of woody plants，and its composition，structure，and formed forest line are extremely sensitive to temperature response；Irrigation has a dynamic relationship of conservation-competition. In the early stage，shrubs provided a good habitat for the settlement of spruce seedlings. In the later period，the shrubs were eliminated by the competition of Qinghai spruce. In the past 100 years （1921-2018），the Qilian Mountain forest line has an obvious upward trend. From the east to the west （Xiying River → Si Dalong → Longchang River），the vertical rise distance of the forest line gradually decreases，and the forest line rises vertically from 40m to 100m.