Northwest China is a difficult and key area for the realization of the dual carbon target strategy due to its arid climate, scarce precipitation, abundant energy and fragile and sensitive ecological environment. The study on its ecosystem carbon sink function and its driving factors is of great significance. Based on the analysis of the evolution of carbon sink land in the past 40 years, this paper reveals the temporal and spatial change law of carbon sink, and deeply explores the relationship between carbon sequestration change and major driving factors such as topography, temperature, and precipitation.The results show that: ① The overall change of land types for carbon sink in northwest China is small, but there are some changes in some parts. ② In 2020, the ecological carbon sinks will be about 58264400 tC/a, of which forest land will dominate, followed by grassland, water area, farmland, wetland and unused land; From large to small, the carbon sinks is Xinjiang, Shaanxi, Gansu, Qinghai, Inner Mongolia (northwest area), Ningxia; The carbon sink intensity is in order of Shaanxi, Gansu, Ningxia, Xinjiang, Qinghai, Inner Mongolia (northwest region). Over the past 40 years, the change of carbon sinks has shown an overall upward trend,and declined in some regions in a certain period. ③ The driving factors of carbon sink mainly include landform, rainfall and temperature. The landform determines the intensity of ecological carbon sink. The intensity of carbon sink is strongly positively correlated with rainfall and positively correlated with temperature.