【Objective】This study aimed to explore the effects of the coupling of different biochar application depths and cropping patterns on the soil carbon pool and crop yield. 【Method】A long-term stationary experiment established in 2019 was adopted, with cropping pattern as the main plot and biochar application method as the subplot. Three cropping patterns were designed: soybean-maize rotation (SM), continuous soybean cropping (S), and continuous maize cropping (M). Three treatments were set up: biochar mixed application at 0-20 cm (B1), biochar mixed application at 0-40 cm (B2), and no biochar application (CK). Soil samples were collected from the 0-20 cm and 20-40 cm soil layers at the crop maturity stage in 2023, and the soil carbon fractions, humus components, and crop yield were determined. 【Result】The results showed that: the contents of soil carbon fractions (e.g., soil organic matter (SOM) and microbial biomass carbon (MBC)) in the rotation system were significantly higher than those in continuous cropping systems, and the SOM content under continuous soybean cropping was significantly higher than that under continuous maize cropping. The application of biochar at 4 500 kg?hm-2 had no significant effect on SOM content in the 0-20 cm soil layer, but it increased the activity of MBC in the 0-20 cm soil layer (by 11.3%-33.7%), optimized humus properties (humic acid (HA) content increased by 6.7%-25.7% while fulvic acid (FA) content decreased by 0.4%-22.5%). This treatment also improved crop yield (soybean yield increased by 24.2%-32.4% and maize yield increased by 13.0%-24.3%). Under the synergistic effect of rotation and biochar application, MBC content increased by 22.8%-33.7%, dissolved organic carbon (DOC) content increased by 17.6%-31.1%, readily oxidizable organic carbon (ROC) content increased by 14.9%-26.6%, HA content increased by 14.5%, FA content increased by 11.8%-15.5%, and the humus quality index (PQ) increased by 11.7%-17.4%.【Conclusion】The coupling of biochar application and crop rotation is beneficial for improving the soil carbon pool, enhancing carbon activity, optimizing humus properties, and increasing crop yield. This practice is expected to play an important role in future agricultural production and soil environment improvement.