Objective <p>To optimize the structure and stability of rice husk biochar through vermiculite modification for improving soil carbon sequestration effects in farmland soils.</p> Materials and methods <p>This study prepared pristine rice husk biochar (RBC) and vermiculite-modified rice husk biochar (V-RBC) using a tube furnace pyrolysis method. Systematic characterization was conducted to investigate the improvement of physicochemical properties of rice husk biochar by vermiculite modification. Subsequently, a 35-day pot experiment was carried out to investigate the impact of vermiculite-modified rice husk biochar on soil carbon sequestration performance.</p> Results and Discussion <p>Vermiculite modification significantly optimized biochar properties, increasing specific surface area by 16.6%, enhancing thermal stability (R₅₀=92.43%), and reducing DOC content by 31.26%. The pot experiment demonstrated that based on a comprehensive analysis of soil fertility, soil aggregate stability, soil organic carbon content, soil enzyme activities, plant growth status, plant photosynthetic carbon sequestration, and soil microbial biomass carbon, 3% vermiculite-modified rice husk biochar (V-RBC) exhibited a significantly better effect on enhancing the overall soil carbon sequestration under dryland maize cultivation compared with unmodified biochar.</p> Conclusion <p>Vermiculite modification significantly improves the soil carbon sequestration performance of rice husk biochar in a dose-dependent manner. The improvement is more obvious under maize dryland conditions, which is a combined result of moisture, crop, and biochar. This study provides theoretical and practical support for agricultural waste utilization and farmland carbon sequestration.</p>