With the acceleration of industrialization, CO₂ and other greenhouse gas emissions have seriously exceeded the standard, which has aggravated global climate change and gradually unbalanced the ecosystem. Vegetation, as an important part of the terrestrial ecosystem, connects natural elements such as atmosphere, soil and water. Collecting CO₂ from the atmosphere and fixing it as organic matter though vegetation photosynthesis has great significance to achieve the goal of sustainable development and carbon neutralization. As the last barrier to protect the ecological security of Northwest China, Helan Mountain not only restrains the eastward movement of Tengger Desert, but also weakens the intrusion of cold current in Northwest China. Its vegetation function is of great significance to regional climate change and ecological security of arid desert zone in north China. However, at present, there are few studies on the carbon sequestration function of vegetation in Helan Mountain. Predecessors either focus on other vegetation parameters or only consider the carbon sequestration ability of a single typical plant. In order to address this issue, based on meteorology, Normalized Difference Vegetation Index (NDVI) and vegetation type data, we used the CASA (Carnegie Ames Stanford Approach) model to estimate the Net Primary Productivity (NPP) and vegetation carbon sequestration in Helan Mountain from 2000 to 2020, then discussed the spatial differentiation characteristics of vegetation carbon sequestration function and its main driving factors. The results showed that:(1) Vegetation carbon sequestration increased significantly from 2000 to 2020, at the same time, vegetation carbon sequestration function was also improved. The spatial distribution features were low all around and high in the middle, low in the west and high in the east, and low in the south and high in the north. (2) Vegetation carbon sequestration increased first and then decreased with the increase of altitude, and there existed obviously different between east and west slopes. With increasing slope, the amount of carbon sequestered per unit area of vegetation on the east and west slopes increased. (3) The driving capacity of vegetation carbon sequestration was different among temperature, precipitation and potential evapotranspiration in the study area. Precipitation was the main driving factor. The conversion of most land use types in Helan Mountain improved carbon sequestration function of vegetation. This study aims to accurately analyze and evaluate the dynamic carbon sequestration function of vegetation under the background of global change and provide a scientific reference for the ecological construction of Helan Mountain.