Based on the forest-grassland-wetland-desert dataset and the Third National Land Survey results, combined with plot surveys and the CBP (Carbon Benefits Project) model, the carbon stock and carbon sink capacity of artificial sand-fixing forests in Gansu Province were quantitatively assessed, and their carbon sink potential was predicted. The results show that currently, the total carbon stock of artificial sand-fixing forests in Gansu Province reaches 2.76×107 t, among which soil carbon stock accounts for 97.46%, dominated by inorganic carbon. The vegetation carbon sink capacity of artificial sand-fixing forests in Gansu Province is 6.27×105 t, with carbon sink value of 1.92×108 yuan; the soil organic carbon sink capacity is 3.00×106 t, with carbon sink value of 9.21×108 yuan; the soil inorganic carbon sink capacity is 1.34×107 t, with carbon sink value of 4.11×109 yuan; the soil carbon sink capacity is 1.64×107 t, with carbon sink value of 5.03×109 yuan; the total carbon sink capacity is 1.70×107 t, with a total carbon sink value of 5.22×109 yuan. Using a vegetation restoration period of 45 a as the baseline, the CBP model estimates the organic carbon sink capacity of artificial sand-fixing forests in Gansu Province to be 3.01×106 t, exhibiting a deviation of 17.08% from the measured value (3.63×106 t), indicating high reliability of the model prediction result. It is predicted that by the end of the seventh phase of the Three-North Shelterbelt Program (in 2050), the total carbon sink capacity of artificial sand-fixing forests in Gansu Province will reach 1.83×108 t, with a total carbon sink value of 5.61×1010 yuan, spatially concentrated in Jiuquan City, Wuwei City, and Zhangye City. It is suggested that establishing artificial sand-fixing forests is a dual-effect strategy for promoting economic development in arid regions and enhancing carbon sink function.