Abstract: The carbon cycle of forest ecosystems plays an important role in the global carbon cycle, which is closely related to CO₂ concentration in atmosphere and has an obvious effect on composition of atmospheric elements. The advances in the studies on carbon cycle of forest ecosystems at home and abroad are reviewed in this paper. The vegetation organic carbon and soil organic carbon pool of forest ecosystems are 359PgC and 1220PgC, accounting for more than 86% of total vegetation carbon organic pool, 73% of soil carbon pool of terrestrial ecosystems, respectively, so the forest ecosystem is a big carbon pool. On the other hand, forest community and forest soil respiration are major ways of carbon dioxide flux from forest ecosystems to atmosphere, which increase the concentration of CO₂ in atmosphere to a certain extent. Soil emission represents the largest terrestrial source of CO₂ to the atmosphere, which has diurnal and seasonal dynamic changes, and is affected by environmental factors such as temperature, humidity, etc., and would actively responses to the increasing concentration of CO₂ in atmosphere. At present, the critical issue in understanding the global carbon cycle is the “missing sink”of CO₂ in atmosphere, being 1.7PgC, which is generally thought to be located in middle latitude region of land in the earth owing to the broad distribution and high productivity of coniferous forest ecosystems. Many researches on carbon cycle models have been done based on varied hypotheses, parametric coefficients and purposes. Proposals on carbon cycle of forest ecosystems and the direction of study in future are presented, which will contribute to a better understanding on the relationship between the global climate changes and forest ecosystems.