Abstract: Based on the peat profile data of ²¹⁰Pb fixed years in Changbai mountain area in recent 200 years, the carbon input rate （p） and decomposition rate （k） in the aerobic decomposition process of active layer peat were estimated by using different decomposition models （single exponential decomposition model, double exponential decomposition model and linear decomposition model） fitting.The effect of p and k on carbon accumulation in peatland was studied by sensitivity analysis. The results showed that the Laolike peat profile in the past 200 years; The organic carbon content varied from 34.4% to 44.8%, and the rate of carbon accumulation （Rate of carbon accumulation, RCA） averaged 79.9 g/（m²·year）. The variation range of organic carbon content in the peat profile of Baijianghe was from 24.4% to 42.5%, and the mean RCA was 62.4 g/（m²·year）. The carbon accumulation massage curves of both profiles were concave, indicating that peat continued to decompose in the past 200 years. Among the three models, the single exponential model had the best fitting effect. According to the simulation results, the carbon input rate of Laolike peatland was 109.940 7 g/（m²·year）, and the decay rate was 0.005 5; Comparatively speaking, the input rate of Baijiang peatland was slightly lower, which was 87.478 8 g/（m²·year）, while the decay rate was faster, which was 0.010 3. Sensitivity analysis showed that under the condition of constant input rate, increasing decay rate will cause the curve to move upward （peat accumulation decreases）; At a constant decomposition rate, a reduction in the input rate would cause the curve to move upwards （a reduction in peat accumulation）. Compared with the decomposition rate, the input rate had more influence on the accumulation of peat.

Key words: peat, carbon accumulation rate, decay model