Abstract: In this paper, the indoor culture experiments were conducted to analyze the content of soil organic carbon and the composition and structural characteristics of soil aggregates under different biochar additions, and to explore the effects of biochar on the composition and stability of soil organic carbon aggregates in forest stand. The results showed that: (1) The total content of soil organic carbon increased with the increase of biochar application. When the amount of biochar was 1%, 2% and 4%, the value could reach 1.2~1.5 times that of the soil without biochar addition. (2) The addition of biochar significantly increased the content of soil particulate organic carbon by 7.8%~64.5% compared with that of the soil without biochar, and the increase was the largest at 2% treatment. Easily oxidized organic carbon followed, with an increase of 0.8%~39.5%, water soluble organic carbon changes the least. (3) The addition of biochar increased the proportion of aggregates with particle sizes >2 mm and 2~>1 mm, and the values of soil MWD, R_>0.25 and AR, which were most obvious at 2% treatment. In conclusion, the addition of biochar could increase the soil organic carbon content of forest soils, promote the formation of soil aggregates and improve the stability of aggregates, which is conducive to the fixation of soil carbon in forest soils, and 2% is the appropriate addition amount of biochar.