As one of major peatlands distributed areas in China, the Sanjiang Plain was studied for many ecological questions like peat mass and carbon stock last several decades. But most researches are analyses based on field samples and sparse field measurements, thus lack in the capability of studying the past and projecting the future. The modeling approach, however, can fill in this gap. This paper aims to calculate the peat mass and carbon stock of Sanjiang Plain during the last 10 ka using a modeling approach. We employed the Holocene Peat Model (HPM), an annual time-step model, to simulate net primary production (NPP), vegetation litter production, litter/peat decomposition and net peat accumulation as a dynamic function of water table depth, nutrient dynamics, vegetation dynamics and peat bulk density profile. Our calculations indicated that in Sanjiang Plain the peat initiation peak was at about 9 ka and 2 ka BP, while 7 ka and 8 ka had few peatlands initiation; since 10 ka BP in Sanjiang Plain, the total accumulated peat mass was about 0.086 Pg (0.074-0.106 Pg), and the accumulated carbon stocks was about 0.025 Pg (0.022-0.031 Pg). Such simulation results qualitatively agree with the observation based on peat core measurements, despite some possible uncertainties in our simulation due to a dearth of driving data and differences in peat properties used in the model. This study was a first attempt of and presented an encouraging potential in applying a dynamic modeling approach for estimating the peat accumulation and carbon stocks in Sanjiang Plain. Therefore, the modeling approach is worth further refining for more accurate understanding of the feedback of peatlands in Sanjiang to the future climate change.