Abstract: In addressing the challenges posed by nutrient-poor and severely degraded yellow-red soil, our study investigated the impact of different biochar types and application rates on the physicochemical properties, extracellular enzyme activities related to carbon and nitrogen cycling, and cluster composition of dryland yellow-red soil. The experiment was set up with eight treatments: no fertilization treatment (CK), conventional fertilization treatment (NPK), and 13.5 t/hm² and 40.5 t/hm² each of corn stover biochar, rice straw biochar and pig manure biochar on the basis of conventional fertilization (CSB1, CSB2, and RSB1, RSB2 as well as PMB1 and PMB2). The results showed that the application of biochar increased the soil organic carbon, total nitrogen, alkali-hydrolyzable nitrogen and total potassium contents to different degrees, ranging from 6.3% to 99.5%, 3.5% to 84.2%, 8.3% to 72.5%, and 2.8% to 15.5%, respectively, compared with the NPK treatment. Application of rice straw biochar and corn stover biochar both decreased soil total phosphorus and available potassium content, while PMB2 treatment increased soil total phosphorus, available phosphorus, available potassium content and cation exchange content by 7.7%, 76.4%, 14.2% and 23.9%, respectively (P<0.05). Application of biochar increased β-xylosidase, β-cellobiohydrolase, Leucine aminopeptidase, and N-acetyl-β-D-glucosaminidase activities by 29.4%～79.1%, 51.6%～264.4%, 4.4%～150.5%, and 45.1%～185.5%, respectively. β-glucosidase activity was decreased by 18.0% and 21.3% in RSB1 and RSB2 treatments (P>0.05), whereas application of both corn stover biochar and pig manure biochar increased β-glucosidase activity. The other biochar treatments had no effect (P>0.05) on 0.25～2 mm agglomerates, except for the PMB1 treatment, which significantly reduced 0.25～2 mm aggregates by 35.0% (P<0.05); none of the biochar applications had a significant effect (P>0.05) on 0.053～0.25 mm aggregates. The application of biochar was able to increase the organic carbon and total nitrogen contents of 0.25～2 mm and 0.053～0.25 mm aggregates to different degrees, among which the PMB2 treatment had the greatest increase (P<0.05), with an increase of 129.54% and 25.2%, 102.87% and 35.1%, respectively. In addition, the application of biochar increased the organic carbon contribution of 0.25～2 mm aggregates to different degrees, and still the PMB2 treatment had the greatest enhancement. In conclusion, the improvement of soil physicochemical properties and enzyme activities by different biochar was shown from largest to smallest as pig manure biochar, corn stover biochar, rice straw biochar, with PMB2 treatment being the most effective. It can be seen that the application of 40.5 t/hm² pig manure biochar can comprehensively improve the physicochemical properties, enzyme activity and carbon and nitrogen content of the aggregates of the yellow-red soil, which is an excellent measure for soil improvement and fertilization of the yellow-red soil of the dryland.