Estimating the carbon budget is one of the most important scientific questions for observing worldwide biological changes. In this study, we used the Integrated Biosphere Simulator (IBIS) to evaluate the effects of climate change and elevated CO₂ concentration on the temporal and spatial variation of carbon budget pattern in the terrestrial ecosystem in China during 1960 to 2006. The results from the model were validated against forestry inventory and flux observation data, and compared with other data from previous publications. The following results were obtained: (1) IBIS accurately simulated the carbon budget pattern of the terrestrial ecosystem of China. The highest net primary productivity (NPP) was observed in southeastern and southwestern China, while the lowest NPP was distributed in northwestern China. (2) The NPP showed an increasing trend from 1960 to 2006 in all climate zones except in the wet-warm-temperate zone. From 1960 to 2006, the total NPP of the terrestrial ecosystem of China showed an increasing trend at a rate of 6 MtC/a and the range of NPP was between 2.2 GtC/a and 2.7 GtC/a, with a mean value of 2.46 GtC/a; peak values occurred in 1990, 1993, 1996, 1998, and 2002. (3) In 11 climate zones, NPP was significantly correlated with precipitation and temperature, and precipitation was the main limiting factor except in the wet-middle temperate, cold temperate, plateau temperate, and plateau frigid zones. (4) The net ecosystem productivity (NEP) showed that most terrestrial ecosystems in China acted as carbon sinks. Only the dry-warm-temperate zone in northwestern China and the southwestern part of the Tibet plateau acted as a small carbon source, while Daxinganling, Xiaoxinganling, and Changbai mountains as well as southeastern and southwestern China acted as large carbon sinks. (5) The NEP showed a significant increasing trend in the wet-middle-temperate, plateau temperate, and plateau frigid zones, while other zones remained in a stable state from 1960 to 2006. The total NEP of the terrestrial ecosystem of China also showed an increasing trend at a rate of 1.6 MtC/a and the range of NEP was between -0.10 GtC/a and 0.25 GtC/a, with a mean value of 0.11 GtC/a from 1960 to 2006. (6) The NEP showed a stronger correlation with precipitation than temperature. Except for temperature, precipitation, increasing CO₂, land-use change, and the program of "Grain for Green" were also among the most important factors caused the change in the carbon budget of China, and the response of terrestrial ecosystem to these factors will be the priority for future research. Above all, IBIS produced reasonable and reliable results on the terrestrial carbon budget in China, and these results can be applied in predicting the potential of carbon sequestration and providing the scientific basis for regional carbon management.