Abstract: Forest ecosystems constitute the main carbon pools in terrestrial ecosystems. It is of great significance to accurately assess the carbon storage of forest ecosystems and determine their distribution characteristics for regional carbon sink management, the scientific formulation of ecological environment protection and land use policies, the promotion of regional low-carbon sustainable development, and the realization of “carbon neutrality”. In this study, the forest ecosystem of the Liulin River Basin, a typical watershed in the Taihang Mountain region, was used as the research object. Based on the sampled land inventory method, the distribution characteristics of carbon density and storage in the forest ecosystems in the region were studied. The results showed that: 1) The carbon density of the forest ecosystem in the Liulin River Basin was 20.80 kg·m⁻², and the carbon storage was 2.95 × 10⁶ t(C). 2) Spatially, the carbon density of forest ecosystems showed an increasing trend with increasing altitude. The carbon density continued to increase from 15.12 kg·m⁻² to 27.34 kg·m⁻² with altitude. The carbon storage initially showed an increasing trend, thereafter decreasing with an increase in altitude, reaching the maximum at an altitude of 700−900 m. Additionally, the average carbon density and the carbon storage of the shady slope was higher than that of the sunny slope. 3) In terms of vertical composition, the carbon storage in the 0−100 cm soil layer in the shrubwood and broad-leaved forests accounted for 77.87% and 51.41% of the total carbon storage in the forest ecosystem, respectively, whereas carbon storage in the vegetation layer was dominant in the coniferous forest, accounting for 53.89%. In coniferous and broad-leaved forests, the carbon density and carbon storage of the tree layer were higher than those of the other vegetation layers. Carbon density and carbon storage in the soil layer of each forest type decreased with increasing soil depth, and carbon storage in the surface soil (0−20 cm) accounted for 69.91% of the total carbon storage in the 0−100 cm soil layer. A gap remains between the carbon density of forest ecosystems in the Liulin River Basin and the average carbon density of forest ecosystems in China. The management of forest ecosystems and the protection and restoration of surface soil in this region, especially in low-altitude and sunny slope areas, will need to be strengthened to enhance forest carbon sequestration and sink capacity. This study not only provides data and theoretical support for carbon storage assessment, ecological restoration, and multi-factor analysis in the Taihang Mountains, but also provides a data and theoretical basis for the management and afforestation of forest ecosystems and carbon sequestration in the Taihang Mountains and similar regions.