[Objective] The change in vegetation cover at different time and the spatial variability of vegetation cover change due to different terrain factors such as elevation, slope, and aspect were analyzed in order to provide reference and data support for the restoration and protection of the ecological environment of the national park of Qilian Mountains. [Methods] Based on remote sensing images of the Qilian Mountains in 2006, 2014, and 2019, the pixel dichotomy model was used to estimate vegetation cover, combined with the trend analysis method and the terrain area correction method in order to analyze the spatial distribution and variation characteristics of vegetation cover under different terrain conditions. [Results] ① Vegetation cover was low in the northwest and high in the southeast of Qilian Mountains. Most of the regions were covered with lower vegetation cover. Vegetation cover showed an increasing trend from 2006 to 2019. The increasing areas accounted for about 46.7% of the total area, and the decreasing areas accounted for about 33.3% of the total area. Vegetation recovery was good during this period. The area of low and lower vegetation cover decreased, while the areas of other cover levels increased to varying degrees. ② There were significant differences in vegetation cover at different elevation ranges: The low-middle elevation areas below 3 200 meters showed an increasing trend, and the low elevation areas below 2 200 meters increased significantly, while the middle-high elevation areas above 3 700 meters showed a decreasing trend. The decreasing trend was more obvious at higher altitudes. ③ As slope increased, the trend in vegetation cover change shifted from increasing to stable, and then turned to decreasing in the steep slopes. The vegetation cover change showed an increasing trend in the areas below 15° and a decreasing trend in the areas above 25°, and the decreasing trend was particularly obvious above 40°. For areas with slopes ranging between 15° and 25°, the distribution of types of vegetation cover change was relatively stable. ④ For the different slope aspects, there were no obvious distribution differences for different vegetation cover change types except in the flat land area. [Conclusion] The effects of elevation and slope factors on vegetation cover change were obvious. However, the effect of aspect factor was not obvious.