Abstract: In order to reveal the influence mechanisms of biochar and decomposed wheat straw on tobacco-planting soil aggregates and to improve tobacco-planting soil effectively, by taking soils from Xuchang tobacco fields as the research object, the stability and organic carbon distribution of soil aggregates in 0-10 cm, 10-20 cm and 20-30 cm soil layers were analyzed under four treatments: conventional fertilization (CK), conventional fertilization + biochar (T1), conventional fertilization + decomposed straw (T2), conventional fertilization + biochar + decomposed straw (T3). The results were as follows: 1) The application of biochar and straw significantly increased the content (mass fraction) of 0.500-1.000 mm aggregates in 0-20 cm soil layer and decreased the content of < 0.250 mm aggregates. Among the four treatments, T3 performed the best. 2) Compared with the control, the application of biochar and straw significantly increased Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD), > 0.250 mm Water-stable Macroaggregate (WR_0.25) and Water Stability Coefficient (K), and significantly reduced Percentage of Aggregate Disruption (PAD), Unstable Aggregate Index (E_LT) and Fractal Dimension (D) in 0-20 cm soil layer; wherein the MWD, GMD, WR_0.25 and K were the highest, while PAD, E_LT and D were the lowest in 0-10 cm soil layer under T3 treatment. 3) The application of biochar and straw significantly increased the organic carbon content in aggregates of various particle sizes in 0-30 cm soil layer, and the organic carbon content in aggregates of various particle sizes was the highest under T1 treatment. 4) The application of biochar and straw improved the contribution rate of organic carbon of large aggregates in 0-30 cm soil layer, and the biochar and straw mixed treatment increased the most. Thereby, the mixed application of biochar and straw can significantly increase the content of macroaggregates and improve the stability of aggregates in 0-20 cm soil layer. The soil total organic carbon content and aggregate organic carbon content in 0-30 cm soil layer can be increased by biochar treatment alone.