Different tillage practices impact soil structure and organic carbon stability in black soil farmland. By comparing conventional tillage with no-tillage, sub-soiling tillage, and moldboard plowing tillage, it was found that no-tillage and sub-soiling tillage increased large aggregates in the topsoil and small aggregates in the subsoil. Large carbon-rich aggregates in no-tillage were especially prominent in the topsoil while sub-soiling and moldboard plowing increased them in the subsoil. Small aggregates contributed significantly to total organic carbon content. No-tillage improved carbon stability in both soil layers. Larger aggregate size positively correlated with organic carbon content and stability. These results help understand how different tillage practices affect soil structure and organic carbon in black soil regions.