Abstract: The Qilian Mountains are an important ecological barrier in northwestern China with rich wildlife resources and landform types, which are situated in the northeastern part of the Qinghai-Tibetan Plateau in China. To investigate the bird composition and vertical distribution characteristics of the southern slope of the Qilian Mountains, this study conducted a comprehensive survey of bird resources across various habitats, seasons, and elevations in May and September 2019 using the line transect method and direct counting method. The results showed that a total of 157 species of birds from 17 orders and 41 families were observed on the southern slopes of the Qilian Mountains, with 95 species (60.51%) of Passeriformes dominating the species composition. The survey recorded 6 species of national first class key protected birds and 17 species of the second class of national protection. In terms of residency type, 81 species (51.59%) were resident birds, 61 species (38.85%) were summer migratory birds, 3 species (1.91%) were winter migratory birds, and 12 species (7.64%) were passage migrants. Palearctic birds dominated the zonal composition with 102 species (64.97%), followed by 34 species (21.66%) of widespread species and 21 species (13.38%) of birds from the Eastern Oceanic boundary. Furthermore, this survey identified the Saxicola ferreus as a newly recorded bird species distributed in Qinghai Province. In seasonal changes, bird community richness, Shannon-Wiener index, Simpson index, and Pielou evenness index were significantly higher in summer compared to autumn (P<0.001). Among the eight classified habitat types, grassland exhibited the highest bird richness (108 species), while desert habitats had the lowest (18 species). Notably, grassland habitat bird communities showed the closest resemblance to wetland habitat bird communities while displaying the least similarity with desert habitat bird communities. Regarding vertical distribution patterns, the bird abundance on the southern slopes displayed the unimodal pattern with increasing altitude, peaking between elevations of 3100 to 3400 meters, and there were significant differences in the structure of bird communities across the altitudinal gradient. In addition, there were seasonal changes in the vertical distribution characteristics of resident birds in the region, with the seasonal change from summer to fall, the vertical distribution range of birds mainly moved downward or upward. Surveying species diversity data serves as the foundation for biodiversity conservation efforts. Understanding the patterns of bird species diversity and their variations along altitude gradients in the region is of great importance for the protection of biodiversity in the southern slopes of the Qilian Mountains.