Abstract: The multisource data from 1981 to 2020 were used, including meteorology, soil, vegetation, remote sensing, etc. The forest carbon cycle model was applied to quantitatively evaluate the dynamic changes in the net primary productivity (NPP), net ecosystem productivity (NEP), and carbon sequestration of Chinese forests. The evaluation was focused on the ecological service function of carbon sequestration in Chinese forests, which is crucial to global sustainable development and the achievement of China’s carbon neutrality goals. The results indicate the following: (1) China’s forest ecosystems served as carbon sinks over the past 40 years. Especially from 2011 to 2020, Chinese forests had an average annual total NEP of 191.44 Tg(C)·a⁻¹ (1 Tg=10¹² g) and an average carbon sequestration of forest per unit area amounting to 0.38 kg(CO₂) m⁻²·a⁻¹. Notable differences were observed in carbon sequestration among different forest types in China. Except for deciduous coniferous forests, other types of forests served as carbon sinks. (2) Overall, climate change over the past 40 years contributed to the carbon sequestration of forest ecosystems in China. Compared with the baseline climate period from 1981 to 2010, the total amount of forest NPP in China increased considerably from 2011 to 2020. The most significant increases in NPP were observed in the southwestern and southeastern forest regions, with increases of 3.10%–6.00%. In addition, forest carbon sequestration in various regions displayed significant differences. High basic spatial distribution characteristics of NPP and NEP of forests per unit area were detected in the Southeast, whereas low values were observed in the Northwest. From 2011 to 2020, a high NPP per unit area was found in the southwestern forest area, followed by the northeastern and southeastern forest areas, whereas a low value was noted in the northwest forest area. Yunnan Province had the highest total NEP of forest, followed by Guangxi and Guangdong. (3) Assessment of the ecological service function of carbon sequestration in Chinese forests based on the constructed meteorological evaluation index for forest carbon sequestration function can well reflect the impacts of meteorological conditions on the ecological service function of forest carbon sequestration. The meteorological conditions from 2019 to 2020 generally favored forest carbon sequestration. Therefore, the ecological service functions of carbon sequestration of forest vegetation during 2019–2020 were better than those of typical years.