The Changbai Mountain range is a well-known and important mountain chain in northeast China, bordering the Korean Peninsula in the south. It is also one of the areas most sensitive to global change. Massive peatlands that play a key role in the global carbon (C) cycle are found in this region. Estimating and assessing C dynamics in Changbai Mountain peatlands is of great importance to local sustainable development. Dry bulk density and C content analyses based on 8 selected peat cores dated by ²¹⁰Pb were used to estimate recent rates of carbon accumulation (RERCA, g C m⁻² yr⁻¹) in Changbai Mountain peatlands. RERCA ranged from 124.2 to 292.8 g C m⁻² yr⁻¹ (average 199.6 ± 60.9 g C m⁻² yr⁻¹). Obvious increasing trends in RERCA were observed in all peat cores. The C pool for 200 years was 38.5–52.1 kg C m⁻², which can supplement the database of C pools for Changbai Mountain ecosystems. The ²¹⁰Pb radiometric technique was tested and found to be a useful study method for recent terrestrial carbon sequestration. This study could contribute to a better understanding of rarely studied mountain peatlands in China and may be useful to global mountain and climate change research.