According to the principles of plant physiology, forest ecology and soil environment，the individual-based carbon budget model of forest ecosystems in china was established. The model process included two timesteps: the primary daily process comprises photosynthesis, plant respiration, allocation and litter production, soil respiration and transfer; the primary annual process consists of allocation between stands, increasing of tree height and breast diameter and producing large amount of litter fall. Through validating NPP and NEP at the plot level and at the country level, it was demonsteated that the model can well simulate carbon budget of forest ecosystem of China, so it can also simulate dynamics of carbon budget of forest ecosystems in the past and in the future.