The Paris Agreement mandates that signatory countries enhance the transparency of their national greenhouse gas inventories. China’s inventories have reported substantial forest carbon gains using ground-based forest plot measurements, but independent satellite-based support for such inventories is lacking and the contributions from human management and anthropogenic environmental changes (atmospheric CO₂ growth, climate change and nitrogen deposition) are unknown. Here we use remote sensing and vegetation modelling to investigate the changes in woody biomass carbon and their drivers across China from 2001 to 2020. Our results show a forest cover increase of 6.2% (59.2 Mha) over this period and a woody biomass carbon sink of 208.6 ± 51.8 TgC yr⁻¹, consistent with the national inventories. The conservation of forest and woodland areas made an unexpectedly large contribution (59.2%) to the observed sink, with an additional 29.4% from anthropogenic expansion. Of these management-driven sinks, 53.7% (99.2 TgC yr⁻¹) is attributed to a direct management effect and the remaining 46.3% to the effects of environmental changes. China’s ecological restoration projects contributed 73.5% of the direct management effect. Our study provides satellite-based evidence to support China’s inventories and underscores the crucial role of human management in the nation’s woody carbon balance.