Abstract: It is crucial to improve our understanding of regional carbon cycling and climate change mitigation by quantifying the contribution of afforestation to regional carbon sequestration. Based on forest resource planning and design data as well as afforestation information from Xingshan County, Hubei, this study applied a regional-scale forest carbon budget model (CBM-CFS3) to simulate and evaluate the impact of afforestation on the carbon stocks and carbon sequestration rates of forest ecosystems in this region from 2009 to 2030 in both afforestation and non-afforestation scenarios. Results show that the average carbon stock and annual carbon sequestration rate of forest ecosystems in this region would be 16 540.55 Gg and 208.04 Gg·a^-1 under afforestation, respectively, representing values that are 472.85 Gg (2.94%) and 16.01 Gg·a^-1 (8.34%) higher than those under BS scenario, respectively. The proportion of carbon stocks in biomass and dead organic matter accounted for 19.11% and 80.89%, respectively; therefore, these two carbon pools contributed 94.15% and 5.85% to the carbon sequestration rate in afforested areas, respectively. Afforestation increased the average carbon stocks of both Pinus massoniana forests and deciduous broad-leaved forests by 237.23 and 235.63 Gg, respectively. This enhanced the carbon sequestration rates of these two forest ecosystems by 6.44 and 9.57 Gg·a^-1, respectively. Afforestation improved forest carbon stocks and carbon sequestration rates by changing the forest age structures in this region. Clearly, planting more deciduous broad-leaved forests and improving forest management will enhance the forest carbon sequestration capability and promote sustainable development of forest resources.