The terrestrial ecosystem carbon sink plays an important role in retarding the increase of atmospheric CO₂concentration and global warming.Affected by human activities and climate change, the terrestrial ecosystem carbon fluxes exhibit strong spatial and temporal variations.Their estimates still have large uncertainties, and the contributions of different factors to their variations are still unclear.Therefore, using the remote-sensing-driven terrestrial ecosystem process model BEPS, the temporal and spatial variation characteristics of global terrestrial ecosystem carbon fluxes from 1981 to 2019 are simulated and analyzed, and the contributions of atmospheric CO₂concentration, leaf area index (LAI), nitrogen deposition and climate change to the change of global terrestrial ecosystem carbon budget are evaluated.From 1981 to 2019, the average values of global terrestrial ecosystem GPP (Gross Primary Productivity), NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) are 115.3, 51.3 and 2.7 Pg·a^-1 (in terms of carbon quality, the same below), and the rising rates are 0.47, 0.21 and 0.06 Pg·a^-1, respectively.GPP and NPP increase significantly in most regions of the world, and the regions where NEP increases significantly (p<0.05) are significantly less than those for GPP and NPP.From 1981 to 2019, the accumulative global NEP is 105.2 Pg.The contributions of forests, savanna and shrub, crop, and grass are 76.4, 15.8, 9.4 and 3.6 Pg, respectively.The accumulative contributions of CO₂ concentration, LAI, nitrogen deposition and climate change to NEP are 58.4, 20.6, 0.7 and -43.6 Pg, respectively.The accumulative contribution of all four factor changes to NEP is 39.8 Pg.The rise of CO₂ concentration is the main contributing factor to the increase of NEP in global terrestrial ecosystem in recent 40 years, followed by LAI.